diff --git a/examples/provider-sync.rs b/examples/provider-sync.rs
index 8bbe9d0..a93dbf5 100644
--- a/examples/provider-sync.rs
+++ b/examples/provider-sync.rs
@@ -3,13 +3,13 @@
 use std::path::Path;
 
 use chrono::{Utc};
+use url::Url;
 
 use kitchen_fridge::{client::Client, traits::CalDavSource};
 use kitchen_fridge::calendar::{CalendarId, SupportedComponents};
 use kitchen_fridge::Item;
 use kitchen_fridge::Task;
 use kitchen_fridge::task::CompletionStatus;
-use kitchen_fridge::item::ItemId;
 use kitchen_fridge::cache::Cache;
 use kitchen_fridge::CalDavProvider;
 use kitchen_fridge::traits::BaseCalendar;
@@ -100,7 +100,7 @@ async fn add_items_and_sync_again(provider: &mut CalDavProvider)
     let changed_calendar_id: CalendarId = EXAMPLE_EXISTING_CALENDAR_URL.parse().unwrap();
     let new_task_name = "This is a new task we're adding as an example, with ÜTF-8 characters";
     let new_task = Task::new(String::from(new_task_name), false, &changed_calendar_id);
-    let new_id = new_task.id().clone();
+    let new_url = new_task.url().clone();
     provider.local().get_calendar(&changed_calendar_id).await.unwrap()
         .lock().unwrap().add_item(Item::Task(new_task)).await.unwrap();
 
@@ -112,20 +112,20 @@ async fn add_items_and_sync_again(provider: &mut CalDavProvider)
     }
     provider.local().save_to_folder().unwrap();
 
-    complete_item_and_sync_again(provider, &changed_calendar_id, &new_id).await;
+    complete_item_and_sync_again(provider, &changed_calendar_id, &new_url).await;
 }
 
 async fn complete_item_and_sync_again(
     provider: &mut CalDavProvider,
     changed_calendar_id: &CalendarId,
-    id_to_complete: &ItemId)
+    url_to_complete: &Url)
 {
     println!("\nNow, we'll mark this last task as completed, and run the sync again.");
     pause();
 
     let completion_status = CompletionStatus::Completed(Some(Utc::now()));
     provider.local().get_calendar(changed_calendar_id).await.unwrap()
-        .lock().unwrap().get_item_by_id_mut(id_to_complete).await.unwrap()
+        .lock().unwrap().get_item_by_id_mut(url_to_complete).await.unwrap()
         .unwrap_task_mut()
         .set_completion_status(completion_status);
 
@@ -136,13 +136,13 @@ async fn complete_item_and_sync_again(
     }
     provider.local().save_to_folder().unwrap();
 
-    remove_items_and_sync_again(provider, changed_calendar_id, id_to_complete).await;
+    remove_items_and_sync_again(provider, changed_calendar_id, url_to_complete).await;
 }
 
 async fn remove_items_and_sync_again(
     provider: &mut CalDavProvider,
     changed_calendar_id: &CalendarId,
-    id_to_remove: &ItemId)
+    id_to_remove: &Url)
 {
     println!("\nNow, we'll delete this last task, and run the sync again.");
     pause();
diff --git a/src/cache.rs b/src/cache.rs
index bc12968..926ec43 100644
--- a/src/cache.rs
+++ b/src/cache.rs
@@ -86,7 +86,7 @@ impl Cache {
                                 continue;
                             },
                             Ok(cal) =>
-                                data.calendars.insert(cal.id().clone(), Arc::new(Mutex::new(cal))),
+                                data.calendars.insert(cal.url().clone(), Arc::new(Mutex::new(cal))),
                         };
                     }
                 },
@@ -259,13 +259,13 @@ mod tests {
 
         {
             let mut bucket_list = bucket_list.lock().unwrap();
-            let cal_id = bucket_list.id().clone();
+            let cal_url = bucket_list.url().clone();
             bucket_list.add_item(Item::Task(Task::new(
-                String::from("Attend a concert of JS Bach"), false, &cal_id
+                String::from("Attend a concert of JS Bach"), false, &cal_url
             ))).await.unwrap();
 
             bucket_list.add_item(Item::Task(Task::new(
-                String::from("Climb the Lighthouse of Alexandria"), true, &cal_id
+                String::from("Climb the Lighthouse of Alexandria"), true, &cal_url
             ))).await.unwrap();
         }
 
diff --git a/src/calendar/cached_calendar.rs b/src/calendar/cached_calendar.rs
index ec4f8a0..aa14db8 100644
--- a/src/calendar/cached_calendar.rs
+++ b/src/calendar/cached_calendar.rs
@@ -4,12 +4,12 @@ use std::error::Error;
 use serde::{Deserialize, Serialize};
 use async_trait::async_trait;
 use csscolorparser::Color;
+use url::Url;
 
 use crate::item::SyncStatus;
 use crate::traits::{BaseCalendar, CompleteCalendar};
 use crate::calendar::{CalendarId, SupportedComponents};
 use crate::Item;
-use crate::item::ItemId;
 
 #[cfg(feature = "local_calendar_mocks_remote_calendars")]
 use std::sync::{Arc, Mutex};
@@ -23,14 +23,14 @@ use crate::mock_behaviour::MockBehaviour;
 #[derive(Clone, Debug, Serialize, Deserialize)]
 pub struct CachedCalendar {
     name: String,
-    id: CalendarId,
+    url: Url,
     supported_components: SupportedComponents,
     color: Option<Color>,
     #[cfg(feature = "local_calendar_mocks_remote_calendars")]
     #[serde(skip)]
     mock_behaviour: Option<Arc<Mutex<MockBehaviour>>>,
 
-    items: HashMap<ItemId, Item>,
+    items: HashMap<Url, Item>,
 }
 
 impl CachedCalendar {
@@ -65,7 +65,7 @@ impl CachedCalendar {
     fn regular_add_or_update_item(&mut self, item: Item) -> Result<SyncStatus, Box<dyn Error>> {
         let ss_clone = item.sync_status().clone();
         log::debug!("Adding or updating an item with {:?}", ss_clone);
-        self.items.insert(item.id().clone(), item);
+        self.items.insert(item.url().clone(), item);
         Ok(ss_clone)
     }
 
@@ -78,7 +78,7 @@ impl CachedCalendar {
             _ => item.set_sync_status(SyncStatus::random_synced()),
         };
         let ss_clone = item.sync_status().clone();
-        self.items.insert(item.id().clone(), item);
+        self.items.insert(item.url().clone(), item);
         Ok(ss_clone)
     }
 
@@ -86,7 +86,7 @@ impl CachedCalendar {
     #[cfg(any(test, feature = "integration_tests"))]
     pub async fn has_same_observable_content_as(&self, other: &CachedCalendar) -> Result<bool, Box<dyn Error>> {
         if self.name != other.name
-        || self.id != other.id
+        || self.url != other.url
         || self.supported_components != other.supported_components
         || self.color != other.color
         {
@@ -119,35 +119,35 @@ impl CachedCalendar {
     }
 
     /// The non-async version of [`Self::get_item_ids`]
-    pub fn get_item_ids_sync(&self) -> Result<HashSet<ItemId>, Box<dyn Error>> {
+    pub fn get_item_ids_sync(&self) -> Result<HashSet<Url>, Box<dyn Error>> {
         Ok(self.items.iter()
-            .map(|(id, _)| id.clone())
+            .map(|(url, _)| url.clone())
             .collect()
         )
     }
 
     /// The non-async version of [`Self::get_items`]
-    pub fn get_items_sync(&self) -> Result<HashMap<ItemId, &Item>, Box<dyn Error>> {
+    pub fn get_items_sync(&self) -> Result<HashMap<Url, &Item>, Box<dyn Error>> {
         Ok(self.items.iter()
-            .map(|(id, item)| (id.clone(), item))
+            .map(|(url, item)| (url.clone(), item))
             .collect()
         )
     }
 
     /// The non-async version of [`Self::get_item_by_id`]
-    pub fn get_item_by_id_sync<'a>(&'a self, id: &ItemId) -> Option<&'a Item> {
+    pub fn get_item_by_id_sync<'a>(&'a self, id: &Url) -> Option<&'a Item> {
         self.items.get(id)
     }
 
     /// The non-async version of [`Self::get_item_by_id_mut`]
-    pub fn get_item_by_id_mut_sync<'a>(&'a mut self, id: &ItemId) -> Option<&'a mut Item> {
+    pub fn get_item_by_id_mut_sync<'a>(&'a mut self, id: &Url) -> Option<&'a mut Item> {
         self.items.get_mut(id)
     }
 
     /// The non-async version of [`Self::add_item`]
     pub fn add_item_sync(&mut self, item: Item) -> Result<SyncStatus, Box<dyn Error>> {
-        if self.items.contains_key(item.id()) {
-            return Err(format!("Item {:?} cannot be added, it exists already", item.id()).into());
+        if self.items.contains_key(item.url()) {
+            return Err(format!("Item {:?} cannot be added, it exists already", item.url()).into());
         }
         #[cfg(not(feature = "local_calendar_mocks_remote_calendars"))]
         return self.regular_add_or_update_item(item);
@@ -158,8 +158,8 @@ impl CachedCalendar {
 
     /// The non-async version of [`Self::update_item`]
     pub fn update_item_sync(&mut self, item: Item) -> Result<SyncStatus, Box<dyn Error>> {
-        if self.items.contains_key(item.id()) == false {
-            return Err(format!("Item {:?} cannot be updated, it does not already exist", item.id()).into());
+        if self.items.contains_key(item.url()) == false {
+            return Err(format!("Item {:?} cannot be updated, it does not already exist", item.url()).into());
         }
         #[cfg(not(feature = "local_calendar_mocks_remote_calendars"))]
         return self.regular_add_or_update_item(item);
@@ -169,7 +169,7 @@ impl CachedCalendar {
     }
 
     /// The non-async version of [`Self::mark_for_deletion`]
-    pub fn mark_for_deletion_sync(&mut self, item_id: &ItemId) -> Result<(), Box<dyn Error>> {
+    pub fn mark_for_deletion_sync(&mut self, item_id: &Url) -> Result<(), Box<dyn Error>> {
         match self.items.get_mut(item_id) {
             None => Err("no item for this key".into()),
             Some(item) => {
@@ -197,7 +197,7 @@ impl CachedCalendar {
     }
 
     /// The non-async version of [`Self::immediately_delete_item`]
-    pub fn immediately_delete_item_sync(&mut self, item_id: &ItemId) -> Result<(), Box<dyn Error>> {
+    pub fn immediately_delete_item_sync(&mut self, item_id: &Url) -> Result<(), Box<dyn Error>> {
         match self.items.remove(item_id) {
             None => Err(format!("Item {} is absent from this calendar", item_id).into()),
             Some(_) => Ok(())
@@ -213,8 +213,8 @@ impl BaseCalendar for CachedCalendar {
         &self.name
     }
 
-    fn id(&self) -> &CalendarId {
-        &self.id
+    fn url(&self) -> &Url {
+        &self.url
     }
 
     fn supported_components(&self) -> SupportedComponents {
@@ -236,36 +236,36 @@ impl BaseCalendar for CachedCalendar {
 
 #[async_trait]
 impl CompleteCalendar for CachedCalendar {
-    fn new(name: String, id: CalendarId, supported_components: SupportedComponents, color: Option<Color>) -> Self {
+    fn new(name: String, url: CalendarId, supported_components: SupportedComponents, color: Option<Color>) -> Self {
         Self {
-            name, id, supported_components, color,
+            name, url, supported_components, color,
             #[cfg(feature = "local_calendar_mocks_remote_calendars")]
             mock_behaviour: None,
             items: HashMap::new(),
         }
     }
 
-    async fn get_item_ids(&self) -> Result<HashSet<ItemId>, Box<dyn Error>> {
+    async fn get_item_ids(&self) -> Result<HashSet<Url>, Box<dyn Error>> {
         self.get_item_ids_sync()
     }
 
-    async fn get_items(&self) -> Result<HashMap<ItemId, &Item>, Box<dyn Error>> {
+    async fn get_items(&self) -> Result<HashMap<Url, &Item>, Box<dyn Error>> {
         self.get_items_sync()
     }
 
-    async fn get_item_by_id<'a>(&'a self, id: &ItemId) -> Option<&'a Item> {
+    async fn get_item_by_id<'a>(&'a self, id: &Url) -> Option<&'a Item> {
         self.get_item_by_id_sync(id)
     }
 
-    async fn get_item_by_id_mut<'a>(&'a mut self, id: &ItemId) -> Option<&'a mut Item> {
+    async fn get_item_by_id_mut<'a>(&'a mut self, id: &Url) -> Option<&'a mut Item> {
         self.get_item_by_id_mut_sync(id)
     }
 
-    async fn mark_for_deletion(&mut self, item_id: &ItemId) -> Result<(), Box<dyn Error>> {
+    async fn mark_for_deletion(&mut self, item_id: &Url) -> Result<(), Box<dyn Error>> {
         self.mark_for_deletion_sync(item_id)
     }
 
-    async fn immediately_delete_item(&mut self, item_id: &ItemId) -> Result<(), Box<dyn Error>> {
+    async fn immediately_delete_item(&mut self, item_id: &Url) -> Result<(), Box<dyn Error>> {
         self.immediately_delete_item_sync(item_id)
     }
 }
@@ -286,7 +286,7 @@ impl DavCalendar for CachedCalendar {
         crate::traits::CompleteCalendar::new(name, resource.url().clone(), supported_components, color)
     }
 
-    async fn get_item_version_tags(&self) -> Result<HashMap<ItemId, VersionTag>, Box<dyn Error>> {
+    async fn get_item_version_tags(&self) -> Result<HashMap<Url, VersionTag>, Box<dyn Error>> {
         #[cfg(feature = "local_calendar_mocks_remote_calendars")]
         self.mock_behaviour.as_ref().map_or(Ok(()), |b| b.lock().unwrap().can_get_item_version_tags())?;
 
@@ -307,14 +307,14 @@ impl DavCalendar for CachedCalendar {
         Ok(result)
     }
 
-    async fn get_item_by_id(&self, id: &ItemId) -> Result<Option<Item>, Box<dyn Error>> {
+    async fn get_item_by_id(&self, id: &Url) -> Result<Option<Item>, Box<dyn Error>> {
         #[cfg(feature = "local_calendar_mocks_remote_calendars")]
         self.mock_behaviour.as_ref().map_or(Ok(()), |b| b.lock().unwrap().can_get_item_by_id())?;
 
         Ok(self.items.get(id).cloned())
     }
 
-    async fn delete_item(&mut self, item_id: &ItemId) -> Result<(), Box<dyn Error>> {
+    async fn delete_item(&mut self, item_id: &Url) -> Result<(), Box<dyn Error>> {
         #[cfg(feature = "local_calendar_mocks_remote_calendars")]
         self.mock_behaviour.as_ref().map_or(Ok(()), |b| b.lock().unwrap().can_delete_item())?;
 
diff --git a/src/calendar/remote_calendar.rs b/src/calendar/remote_calendar.rs
index 14912d4..050c78a 100644
--- a/src/calendar/remote_calendar.rs
+++ b/src/calendar/remote_calendar.rs
@@ -5,13 +5,12 @@ use std::sync::Mutex;
 use async_trait::async_trait;
 use reqwest::{header::CONTENT_TYPE, header::CONTENT_LENGTH};
 use csscolorparser::Color;
+use url::Url;
 
 use crate::traits::BaseCalendar;
 use crate::traits::DavCalendar;
 use crate::calendar::SupportedComponents;
-use crate::calendar::CalendarId;
 use crate::item::Item;
-use crate::item::ItemId;
 use crate::item::VersionTag;
 use crate::item::SyncStatus;
 use crate::resource::Resource;
@@ -40,13 +39,13 @@ pub struct RemoteCalendar {
     supported_components: SupportedComponents,
     color: Option<Color>,
 
-    cached_version_tags: Mutex<Option<HashMap<ItemId, VersionTag>>>,
+    cached_version_tags: Mutex<Option<HashMap<Url, VersionTag>>>,
 }
 
 #[async_trait]
 impl BaseCalendar for RemoteCalendar {
     fn name(&self) -> &str { &self.name }
-    fn id(&self) -> &CalendarId { &self.resource.url() }
+    fn url(&self) -> &Url { &self.resource.url() }
     fn supported_components(&self) -> crate::calendar::SupportedComponents {
         self.supported_components
     }
@@ -58,7 +57,7 @@ impl BaseCalendar for RemoteCalendar {
         let ical_text = crate::ical::build_from(&item)?;
 
         let response = reqwest::Client::new()
-            .put(item.id().as_url().clone())
+            .put(item.url().clone())
             .header("If-None-Match", "*")
             .header(CONTENT_TYPE, "text/calendar")
             .header(CONTENT_LENGTH, ical_text.len())
@@ -73,7 +72,7 @@ impl BaseCalendar for RemoteCalendar {
 
         let reply_hdrs = response.headers();
         match reply_hdrs.get("ETag") {
-            None => Err(format!("No ETag in these response headers: {:?} (request was {:?})", reply_hdrs, item.id()).into()),
+            None => Err(format!("No ETag in these response headers: {:?} (request was {:?})", reply_hdrs, item.url()).into()),
             Some(etag) => {
                 let vtag_str = etag.to_str()?;
                 let vtag = VersionTag::from(String::from(vtag_str));
@@ -92,7 +91,7 @@ impl BaseCalendar for RemoteCalendar {
         let ical_text = crate::ical::build_from(&item)?;
 
         let request = reqwest::Client::new()
-            .put(item.id().as_url().clone())
+            .put(item.url().clone())
             .header("If-Match", old_etag.as_str())
             .header(CONTENT_TYPE, "text/calendar")
             .header(CONTENT_LENGTH, ical_text.len())
@@ -107,7 +106,7 @@ impl BaseCalendar for RemoteCalendar {
 
         let reply_hdrs = request.headers();
         match reply_hdrs.get("ETag") {
-            None => Err(format!("No ETag in these response headers: {:?} (request was {:?})", reply_hdrs, item.id()).into()),
+            None => Err(format!("No ETag in these response headers: {:?} (request was {:?})", reply_hdrs, item.url()).into()),
             Some(etag) => {
                 let vtag_str = etag.to_str()?;
                 let vtag = VersionTag::from(String::from(vtag_str));
@@ -127,7 +126,7 @@ impl DavCalendar for RemoteCalendar {
     }
 
 
-    async fn get_item_version_tags(&self) -> Result<HashMap<ItemId, VersionTag>, Box<dyn Error>> {
+    async fn get_item_version_tags(&self) -> Result<HashMap<Url, VersionTag>, Box<dyn Error>> {
         if let Some(map) = &*self.cached_version_tags.lock().unwrap() {
             log::debug!("Version tags are already cached.");
             return Ok(map.clone());
@@ -145,7 +144,7 @@ impl DavCalendar for RemoteCalendar {
                     continue;
                 },
                 Some(resource) => {
-                    ItemId::from(&resource)
+                    resource.url().clone()
                 },
             };
 
@@ -159,7 +158,7 @@ impl DavCalendar for RemoteCalendar {
                 }
             };
 
-            items.insert(item_id, version_tag);
+            items.insert(item_id.clone(), version_tag);
         }
 
         // Note: the mutex cannot be locked during this whole async function, but it can safely be re-entrant (this will just waste an unnecessary request)
@@ -167,9 +166,9 @@ impl DavCalendar for RemoteCalendar {
         Ok(items)
     }
 
-    async fn get_item_by_id(&self, id: &ItemId) -> Result<Option<Item>, Box<dyn Error>> {
+    async fn get_item_by_id(&self, id: &Url) -> Result<Option<Item>, Box<dyn Error>> {
         let res = reqwest::Client::new()
-            .get(id.as_url().clone())
+            .get(id.clone())
             .header(CONTENT_TYPE, "text/calendar")
             .basic_auth(self.resource.username(), Some(self.resource.password()))
             .send()
@@ -192,9 +191,9 @@ impl DavCalendar for RemoteCalendar {
         Ok(Some(item))
     }
 
-    async fn delete_item(&mut self, item_id: &ItemId) -> Result<(), Box<dyn Error>> {
+    async fn delete_item(&mut self, item_id: &Url) -> Result<(), Box<dyn Error>> {
         let del_response = reqwest::Client::new()
-            .delete(item_id.as_url().clone())
+            .delete(item_id.clone())
             .basic_auth(self.resource.username(), Some(self.resource.password()))
             .send()
             .await?;
diff --git a/src/client.rs b/src/client.rs
index 112fdc0..242a1a1 100644
--- a/src/client.rs
+++ b/src/client.rs
@@ -216,7 +216,7 @@ impl Client {
 
             let this_calendar = RemoteCalendar::new(display_name, this_calendar_url, supported_components, this_calendar_color);
             log::info!("Found calendar {}", this_calendar.name());
-            calendars.insert(this_calendar.id().clone(), Arc::new(Mutex::new(this_calendar)));
+            calendars.insert(this_calendar.url().clone(), Arc::new(Mutex::new(this_calendar)));
         }
 
         let mut replies = self.cached_replies.lock().unwrap();
diff --git a/src/event.rs b/src/event.rs
index c2149ca..2821242 100644
--- a/src/event.rs
+++ b/src/event.rs
@@ -2,15 +2,15 @@
 
 use serde::{Deserialize, Serialize};
 use chrono::{DateTime, Utc};
+use url::Url;
 
-use crate::item::ItemId;
 use crate::item::SyncStatus;
 
 /// TODO: implement `Event` one day.
 /// This crate currently only supports tasks, not calendar events.
 #[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
 pub struct Event {
-    id: ItemId,
+    uid: String,
     name: String,
     sync_status: SyncStatus,
 }
@@ -20,12 +20,12 @@ impl Event {
         unimplemented!();
     }
 
-    pub fn id(&self) -> &ItemId {
-        &self.id
+    pub fn url(&self) -> &Url {
+        unimplemented!();
     }
 
     pub fn uid(&self) -> &str {
-        unimplemented!()
+        &self.uid
     }
 
     pub fn name(&self) -> &str {
diff --git a/src/ical/parser.rs b/src/ical/parser.rs
index 8be5da5..3bdeadd 100644
--- a/src/ical/parser.rs
+++ b/src/ical/parser.rs
@@ -4,22 +4,22 @@ use std::error::Error;
 
 use ical::parser::ical::component::{IcalCalendar, IcalEvent, IcalTodo};
 use chrono::{DateTime, TimeZone, Utc};
+use url::Url;
 
 use crate::Item;
 use crate::item::SyncStatus;
-use crate::item::ItemId;
 use crate::Task;
 use crate::task::CompletionStatus;
 use crate::Event;
 
 
 /// Parse an iCal file into the internal representation [`crate::Item`]
-pub fn parse(content: &str, item_id: ItemId, sync_status: SyncStatus) -> Result<Item, Box<dyn Error>> {
+pub fn parse(content: &str, item_url: Url, sync_status: SyncStatus) -> Result<Item, Box<dyn Error>> {
     let mut reader = ical::IcalParser::new(content.as_bytes());
     let parsed_item = match reader.next() {
-        None => return Err(format!("Invalid iCal data to parse for item {}", item_id).into()),
+        None => return Err(format!("Invalid iCal data to parse for item {}", item_url).into()),
         Some(item) => match item {
-            Err(err) => return Err(format!("Unable to parse iCal data for item {}: {}", item_id, err).into()),
+            Err(err) => return Err(format!("Unable to parse iCal data for item {}: {}", item_url, err).into()),
             Ok(item) => item,
         }
     };
@@ -80,15 +80,15 @@ pub fn parse(content: &str, item_id: ItemId, sync_status: SyncStatus) -> Result<
             }
             let name = match name {
                 Some(name) => name,
-                None => return Err(format!("Missing name for item {}", item_id).into()),
+                None => return Err(format!("Missing name for item {}", item_url).into()),
             };
             let uid = match uid {
                 Some(uid) => uid,
-                None => return Err(format!("Missing UID for item {}", item_id).into()),
+                None => return Err(format!("Missing UID for item {}", item_url).into()),
             };
             let last_modified = match last_modified {
                 Some(dt) => dt,
-                None => return Err(format!("Missing DTSTAMP for item {}, but this is required by RFC5545", item_id).into()),
+                None => return Err(format!("Missing DTSTAMP for item {}, but this is required by RFC5545", item_url).into()),
             };
             let completion_status = match completed {
                 false => {
@@ -100,7 +100,7 @@ pub fn parse(content: &str, item_id: ItemId, sync_status: SyncStatus) -> Result<
                 true => CompletionStatus::Completed(completion_date),
             };
 
-            Item::Task(Task::new_with_parameters(name, uid, item_id, completion_status, sync_status, creation_date, last_modified, ical_prod_id, extra_parameters))
+            Item::Task(Task::new_with_parameters(name, uid, item_url, completion_status, sync_status, creation_date, last_modified, ical_prod_id, extra_parameters))
         },
     };
 
@@ -244,13 +244,13 @@ END:VCALENDAR
     fn test_ical_parsing() {
         let version_tag = VersionTag::from(String::from("test-tag"));
         let sync_status = SyncStatus::Synced(version_tag);
-        let item_id: ItemId = "http://some.id/for/testing".parse().unwrap();
+        let item_url: Url = "http://some.id/for/testing".parse().unwrap();
 
-        let item = parse(EXAMPLE_ICAL, item_id.clone(), sync_status.clone()).unwrap();
+        let item = parse(EXAMPLE_ICAL, item_url.clone(), sync_status.clone()).unwrap();
         let task = item.unwrap_task();
 
         assert_eq!(task.name(), "Do not forget to do this");
-        assert_eq!(task.id(), &item_id);
+        assert_eq!(task.url(), &item_url);
         assert_eq!(task.uid(), "0633de27-8c32-42be-bcb8-63bc879c6185@some-domain.com");
         assert_eq!(task.completed(), false);
         assert_eq!(task.completion_status(), &CompletionStatus::Uncompleted);
@@ -262,9 +262,9 @@ END:VCALENDAR
     fn test_completed_ical_parsing() {
         let version_tag = VersionTag::from(String::from("test-tag"));
         let sync_status = SyncStatus::Synced(version_tag);
-        let item_id: ItemId = "http://some.id/for/testing".parse().unwrap();
+        let item_url: Url = "http://some.id/for/testing".parse().unwrap();
 
-        let item = parse(EXAMPLE_ICAL_COMPLETED, item_id.clone(), sync_status.clone()).unwrap();
+        let item = parse(EXAMPLE_ICAL_COMPLETED, item_url.clone(), sync_status.clone()).unwrap();
         let task = item.unwrap_task();
 
         assert_eq!(task.completed(), true);
@@ -275,9 +275,9 @@ END:VCALENDAR
     fn test_completed_without_date_ical_parsing() {
         let version_tag = VersionTag::from(String::from("test-tag"));
         let sync_status = SyncStatus::Synced(version_tag);
-        let item_id: ItemId = "http://some.id/for/testing".parse().unwrap();
+        let item_url: Url = "http://some.id/for/testing".parse().unwrap();
 
-        let item = parse(EXAMPLE_ICAL_COMPLETED_WITHOUT_A_COMPLETION_DATE, item_id.clone(), sync_status.clone()).unwrap();
+        let item = parse(EXAMPLE_ICAL_COMPLETED_WITHOUT_A_COMPLETION_DATE, item_url.clone(), sync_status.clone()).unwrap();
         let task = item.unwrap_task();
 
         assert_eq!(task.completed(), true);
@@ -288,9 +288,9 @@ END:VCALENDAR
     fn test_multiple_items_in_ical() {
         let version_tag = VersionTag::from(String::from("test-tag"));
         let sync_status = SyncStatus::Synced(version_tag);
-        let item_id: ItemId = "http://some.id/for/testing".parse().unwrap();
+        let item_url: Url = "http://some.id/for/testing".parse().unwrap();
 
-        let item = parse(EXAMPLE_MULTIPLE_ICAL, item_id.clone(), sync_status.clone());
+        let item = parse(EXAMPLE_MULTIPLE_ICAL, item_url.clone(), sync_status.clone());
         assert!(item.is_err());
     }
 }
diff --git a/src/item.rs b/src/item.rs
index 9c45056..8d457d0 100644
--- a/src/item.rs
+++ b/src/item.rs
@@ -1,17 +1,10 @@
 //! CalDAV items (todo, events, journals...)
 // TODO: move Event and Task to nest them in crate::items::calendar::Calendar?
 
-use std::fmt::{Display, Formatter};
-use std::str::FromStr;
-
-use serde::{Deserialize, Deserializer, Serialize, Serializer};
+use serde::{Deserialize, Serialize};
 use url::Url;
 use chrono::{DateTime, Utc};
 
-use crate::resource::Resource;
-use crate::calendar::CalendarId;
-
-
 
 #[derive(Clone, Debug, Serialize, Deserialize)]
 pub enum Item {
@@ -32,7 +25,7 @@ macro_rules! synthetise_common_getter {
 }
 
 impl Item {
-    synthetise_common_getter!(id, &ItemId);
+    synthetise_common_getter!(url, &Url);
     synthetise_common_getter!(uid, &str);
     synthetise_common_getter!(name, &str);
     synthetise_common_getter!(creation_date, Option<&DateTime<Utc>>);
@@ -94,67 +87,6 @@ impl Item {
 }
 
 
-#[derive(Clone, Debug, PartialEq, Hash)]
-pub struct ItemId {
-    content: Url,
-}
-impl ItemId{
-    /// Generate a random ItemId.
-    pub fn random(parent_calendar: &CalendarId) -> Self {
-        let random = uuid::Uuid::new_v4().to_hyphenated().to_string();
-        let u = parent_calendar.join(&random).unwrap(/* this cannot panic since we've just created a string that is a valid URL */);
-        Self { content:u }
-    }
-
-    pub fn as_url(&self) -> &Url {
-        &self.content
-    }
-}
-impl From<Url> for ItemId {
-    fn from(url: Url) -> Self {
-        Self { content: url }
-    }
-}
-impl From<&Resource> for ItemId {
-    fn from(resource: &Resource) -> Self {
-        Self { content: resource.url().clone() }
-    }
-}
-impl FromStr for ItemId {
-    type Err = url::ParseError;
-    fn from_str(s: &str) -> Result<Self, Self::Err> {
-        let u: Url = s.parse()?;
-        Ok(Self::from(u))
-    }
-}
-
-impl Eq for ItemId {}
-impl Display for ItemId {
-    fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), std::fmt::Error> {
-        write!(f, "{}", self.content)
-    }
-}
-
-/// Used to support serde
-impl Serialize for ItemId {
-    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-    where
-        S: Serializer,
-    {
-        serializer.serialize_str(self.content.as_str())
-    }
-}
-/// Used to support serde
-impl<'de> Deserialize<'de> for ItemId {
-    fn deserialize<D>(deserializer: D) -> Result<ItemId, D::Error>
-    where
-        D: Deserializer<'de>,
-    {
-        let u = Url::deserialize(deserializer)?;
-        Ok(ItemId{ content: u })
-    }
-}
-
 
 
 /// A VersionTag is basically a CalDAV `ctag` or `etag`. Whenever it changes, this means the data has changed.
diff --git a/src/provider/mod.rs b/src/provider/mod.rs
index 6bb9a5e..2e9fb84 100644
--- a/src/provider/mod.rs
+++ b/src/provider/mod.rs
@@ -6,10 +6,11 @@ use std::error::Error;
 use std::collections::HashSet;
 use std::marker::PhantomData;
 use std::sync::{Arc, Mutex};
+use url::Url;
 
 use crate::traits::{BaseCalendar, CalDavSource, DavCalendar};
 use crate::traits::CompleteCalendar;
-use crate::item::{ItemId, SyncStatus};
+use crate::item::SyncStatus;
 use crate::calendar::CalendarId;
 
 pub mod sync_progress;
@@ -400,7 +401,7 @@ where
     }
 
 
-    async fn item_name(cal: &T, id: &ItemId) -> String {
+    async fn item_name(cal: &T, id: &Url) -> String {
         cal.get_item_by_id(id).await.map(|item| item.name()).unwrap_or_default().to_string()
     }
 
diff --git a/src/task.rs b/src/task.rs
index 91e180a..4da9d93 100644
--- a/src/task.rs
+++ b/src/task.rs
@@ -4,10 +4,11 @@ use serde::{Deserialize, Serialize};
 use uuid::Uuid;
 use chrono::{DateTime, Utc};
 use ical::property::Property;
+use url::Url;
 
-use crate::item::ItemId;
 use crate::item::SyncStatus;
 use crate::calendar::CalendarId;
+use crate::utils::random_url;
 
 /// RFC5545 defines the completion as several optional fields, yet some combinations make no sense.
 /// This enum provides an API that forbids such impossible combinations.
@@ -33,10 +34,11 @@ impl CompletionStatus {
 #[derive(Clone, Debug, Serialize, Deserialize)]
 pub struct Task {
     /// The task URL
-    id: ItemId,
+    url: Url,
 
     /// Persistent, globally unique identifier for the calendar component
-    /// The [RFC](https://tools.ietf.org/html/rfc5545#page-117) recommends concatenating a timestamp with the server's domain name, but UUID are even better
+    /// The [RFC](https://tools.ietf.org/html/rfc5545#page-117) recommends concatenating a timestamp with the server's domain name.
+    /// UUID are even better so we'll generate them, but we have to support tasks from the server, that may have any arbitrary strings here.
     uid: String,
 
     /// The sync status of this item
@@ -65,8 +67,8 @@ pub struct Task {
 impl Task {
     /// Create a brand new Task that is not on a server yet.
     /// This will pick a new (random) task ID.
-    pub fn new(name: String, completed: bool, parent_calendar_id: &CalendarId) -> Self {
-        let new_item_id = ItemId::random(parent_calendar_id);
+    pub fn new(name: String, completed: bool, parent_calendar_url: &CalendarId) -> Self {
+        let new_url = random_url(parent_calendar_url);
         let new_sync_status = SyncStatus::NotSynced;
         let new_uid = Uuid::new_v4().to_hyphenated().to_string();
         let new_creation_date = Some(Utc::now());
@@ -76,18 +78,18 @@ impl Task {
             } else { CompletionStatus::Uncompleted };
         let ical_prod_id = crate::ical::default_prod_id();
         let extra_parameters = Vec::new();
-        Self::new_with_parameters(name, new_uid, new_item_id, new_completion_status, new_sync_status, new_creation_date, new_last_modified, ical_prod_id, extra_parameters)
+        Self::new_with_parameters(name, new_uid, new_url, new_completion_status, new_sync_status, new_creation_date, new_last_modified, ical_prod_id, extra_parameters)
     }
 
     /// Create a new Task instance, that may be synced on the server already
-    pub fn new_with_parameters(name: String, uid: String, id: ItemId,
+    pub fn new_with_parameters(name: String, uid: String, new_url: Url,
                                completion_status: CompletionStatus,
                                sync_status: SyncStatus, creation_date: Option<DateTime<Utc>>, last_modified: DateTime<Utc>,
                                ical_prod_id: String, extra_parameters: Vec<Property>,
                             ) -> Self
     {
         Self {
-            id,
+            url: new_url,
             uid,
             name,
             completion_status,
@@ -99,7 +101,7 @@ impl Task {
         }
     }
 
-    pub fn id(&self) -> &ItemId     { &self.id          }
+    pub fn url(&self) -> &Url       { &self.url         }
     pub fn uid(&self) -> &str       { &self.uid         }
     pub fn name(&self) -> &str      { &self.name        }
     pub fn completed(&self) -> bool { self.completion_status.is_completed() }
@@ -112,7 +114,8 @@ impl Task {
 
     #[cfg(any(test, feature = "integration_tests"))]
     pub fn has_same_observable_content_as(&self, other: &Task) -> bool {
-           self.id == other.id
+           self.url == other.url
+        && self.uid == other.uid
         && self.name == other.name
         // sync status must be the same variant, but we ignore its embedded version tag
         && std::mem::discriminant(&self.sync_status) == std::mem::discriminant(&other.sync_status)
diff --git a/src/traits.rs b/src/traits.rs
index 5dc1bd4..66c1b43 100644
--- a/src/traits.rs
+++ b/src/traits.rs
@@ -6,10 +6,10 @@ use std::sync::{Arc, Mutex};
 
 use async_trait::async_trait;
 use csscolorparser::Color;
+use url::Url;
 
 use crate::item::SyncStatus;
 use crate::item::Item;
-use crate::item::ItemId;
 use crate::item::VersionTag;
 use crate::calendar::CalendarId;
 use crate::calendar::SupportedComponents;
@@ -40,8 +40,8 @@ pub trait BaseCalendar {
     /// Returns the calendar name
     fn name(&self) -> &str;
 
-    /// Returns the calendar unique ID
-    fn id(&self) -> &CalendarId;
+    /// Returns the calendar URL
+    fn url(&self) -> &Url;
 
     /// Returns the supported kinds of components for this calendar
     fn supported_components(&self) -> crate::calendar::SupportedComponents;
@@ -79,16 +79,16 @@ pub trait DavCalendar : BaseCalendar {
     fn new(name: String, resource: Resource, supported_components: SupportedComponents, color: Option<Color>) -> Self;
 
     /// Get the IDs and the version tags of every item in this calendar
-    async fn get_item_version_tags(&self) -> Result<HashMap<ItemId, VersionTag>, Box<dyn Error>>;
+    async fn get_item_version_tags(&self) -> Result<HashMap<Url, VersionTag>, Box<dyn Error>>;
 
     /// Returns a particular item
-    async fn get_item_by_id(&self, id: &ItemId) -> Result<Option<Item>, Box<dyn Error>>;
+    async fn get_item_by_id(&self, id: &Url) -> Result<Option<Item>, Box<dyn Error>>;
 
     /// Delete an item
-    async fn delete_item(&mut self, item_id: &ItemId) -> Result<(), Box<dyn Error>>;
+    async fn delete_item(&mut self, item_id: &Url) -> Result<(), Box<dyn Error>>;
 
     /// Get the IDs of all current items in this calendar
-    async fn get_item_ids(&self) -> Result<HashSet<ItemId>, Box<dyn Error>> {
+    async fn get_item_ids(&self) -> Result<HashSet<Url>, Box<dyn Error>> {
         let items = self.get_item_version_tags().await?;
         Ok(items.iter()
             .map(|(id, _tag)| id.clone())
@@ -111,22 +111,22 @@ pub trait CompleteCalendar : BaseCalendar {
     fn new(name: String, id: CalendarId, supported_components: SupportedComponents, color: Option<Color>) -> Self;
 
     /// Get the IDs of all current items in this calendar
-    async fn get_item_ids(&self) -> Result<HashSet<ItemId>, Box<dyn Error>>;
+    async fn get_item_ids(&self) -> Result<HashSet<Url>, Box<dyn Error>>;
 
     /// Returns all items that this calendar contains
-    async fn get_items(&self) -> Result<HashMap<ItemId, &Item>, Box<dyn Error>>;
+    async fn get_items(&self) -> Result<HashMap<Url, &Item>, Box<dyn Error>>;
 
     /// Returns a particular item
-    async fn get_item_by_id<'a>(&'a self, id: &ItemId) -> Option<&'a Item>;
+    async fn get_item_by_id<'a>(&'a self, id: &Url) -> Option<&'a Item>;
 
     /// Returns a particular item
-    async fn get_item_by_id_mut<'a>(&'a mut self, id: &ItemId) -> Option<&'a mut Item>;
+    async fn get_item_by_id_mut<'a>(&'a mut self, id: &Url) -> Option<&'a mut Item>;
 
     /// Mark an item for deletion.
     /// This is required so that the upcoming sync will know it should also also delete this task from the server
     /// (and then call [`CompleteCalendar::immediately_delete_item`] once it has been successfully deleted on the server)
-    async fn mark_for_deletion(&mut self, item_id: &ItemId) -> Result<(), Box<dyn Error>>;
+    async fn mark_for_deletion(&mut self, item_id: &Url) -> Result<(), Box<dyn Error>>;
 
     /// Immediately remove an item. See [`CompleteCalendar::mark_for_deletion`]
-    async fn immediately_delete_item(&mut self, item_id: &ItemId) -> Result<(), Box<dyn Error>>;
+    async fn immediately_delete_item(&mut self, item_id: &Url) -> Result<(), Box<dyn Error>>;
 }
diff --git a/src/utils/mod.rs b/src/utils/mod.rs
index 9aba3a5..68f1c69 100644
--- a/src/utils/mod.rs
+++ b/src/utils/mod.rs
@@ -6,6 +6,7 @@ use std::hash::Hash;
 use std::io::{stdin, stdout, Read, Write};
 
 use minidom::Element;
+use url::Url;
 
 use crate::traits::CompleteCalendar;
 use crate::traits::DavCalendar;
@@ -107,7 +108,7 @@ pub fn print_task(item: &Item) {
                 SyncStatus::LocallyModified(_) => "~",
                 SyncStatus::LocallyDeleted(_) =>  "x",
             };
-            println!("    {}{} {}\t{}", completion, sync, task.name(), task.id());
+            println!("    {}{} {}\t{}", completion, sync, task.name(), task.url());
         },
         _ => return,
     }
@@ -148,3 +149,10 @@ pub fn pause() {
     stdout.flush().unwrap();
     stdin().read_exact(&mut [0]).unwrap();
 }
+
+
+/// Generate a random URL with a given prefix
+pub fn random_url(parent_calendar: &Url) -> Url {
+    let random = uuid::Uuid::new_v4().to_hyphenated().to_string();
+    parent_calendar.join(&random).unwrap(/* this cannot panic since we've just created a string that is a valid URL */)
+}
diff --git a/tests/scenarii.rs b/tests/scenarii.rs
index 5888997..8987c8b 100644
--- a/tests/scenarii.rs
+++ b/tests/scenarii.rs
@@ -11,6 +11,7 @@
 use std::path::PathBuf;
 use std::sync::{Arc, Mutex};
 use std::error::Error;
+use url::Url;
 
 use chrono::Utc;
 
@@ -22,13 +23,13 @@ use kitchen_fridge::traits::CompleteCalendar;
 use kitchen_fridge::traits::DavCalendar;
 use kitchen_fridge::cache::Cache;
 use kitchen_fridge::Item;
-use kitchen_fridge::item::ItemId;
 use kitchen_fridge::item::SyncStatus;
 use kitchen_fridge::Task;
 use kitchen_fridge::task::CompletionStatus;
 use kitchen_fridge::calendar::cached_calendar::CachedCalendar;
 use kitchen_fridge::provider::Provider;
 use kitchen_fridge::mock_behaviour::MockBehaviour;
+use kitchen_fridge::utils::random_url;
 
 pub enum LocatedState {
     /// Item does not exist yet or does not exist anymore
@@ -62,7 +63,7 @@ pub enum ChangeToApply {
 
 
 pub struct ItemScenario {
-    id: ItemId,
+    url: Url,
     initial_state: LocatedState,
     local_changes_to_apply:  Vec<ChangeToApply>,
     remote_changes_to_apply: Vec<ChangeToApply>,
@@ -93,7 +94,7 @@ pub fn scenarii_basic() -> Vec<ItemScenario> {
 
     tasks.push(
         ItemScenario {
-            id: ItemId::random(&first_cal),
+            url: random_url(&first_cal),
             initial_state: LocatedState::BothSynced( ItemState{
                 calendar: first_cal.clone(),
                 name: String::from("Task A"),
@@ -111,7 +112,7 @@ pub fn scenarii_basic() -> Vec<ItemScenario> {
 
     tasks.push(
         ItemScenario {
-            id: ItemId::random(&first_cal),
+            url: random_url(&first_cal),
             initial_state: LocatedState::BothSynced( ItemState{
                 calendar: first_cal.clone(),
                 name: String::from("Task B"),
@@ -125,7 +126,7 @@ pub fn scenarii_basic() -> Vec<ItemScenario> {
 
     tasks.push(
         ItemScenario {
-            id: ItemId::random(&first_cal),
+            url: random_url(&first_cal),
             initial_state: LocatedState::BothSynced( ItemState{
                 calendar: first_cal.clone(),
                 name: String::from("Task C"),
@@ -139,7 +140,7 @@ pub fn scenarii_basic() -> Vec<ItemScenario> {
 
     tasks.push(
         ItemScenario {
-            id: ItemId::random(&first_cal),
+            url: random_url(&first_cal),
             initial_state: LocatedState::BothSynced( ItemState{
                 calendar: first_cal.clone(),
                 name: String::from("Task D"),
@@ -157,7 +158,7 @@ pub fn scenarii_basic() -> Vec<ItemScenario> {
 
     tasks.push(
         ItemScenario {
-            id: ItemId::random(&first_cal),
+            url: random_url(&first_cal),
             initial_state: LocatedState::BothSynced( ItemState{
                 calendar: first_cal.clone(),
                 name: String::from("Task E"),
@@ -175,7 +176,7 @@ pub fn scenarii_basic() -> Vec<ItemScenario> {
 
     tasks.push(
         ItemScenario {
-            id: ItemId::random(&first_cal),
+            url: random_url(&first_cal),
             initial_state: LocatedState::BothSynced( ItemState{
                 calendar: first_cal.clone(),
                 name: String::from("Task F"),
@@ -194,7 +195,7 @@ pub fn scenarii_basic() -> Vec<ItemScenario> {
 
     tasks.push(
         ItemScenario {
-            id: ItemId::random(&second_cal),
+            url: random_url(&second_cal),
             initial_state: LocatedState::BothSynced( ItemState{
                 calendar: second_cal.clone(),
                 name: String::from("Task G"),
@@ -212,7 +213,7 @@ pub fn scenarii_basic() -> Vec<ItemScenario> {
 
     tasks.push(
         ItemScenario {
-            id: ItemId::random(&second_cal),
+            url: random_url(&second_cal),
             initial_state: LocatedState::BothSynced( ItemState{
                 calendar: second_cal.clone(),
                 name: String::from("Task H"),
@@ -230,7 +231,7 @@ pub fn scenarii_basic() -> Vec<ItemScenario> {
 
     tasks.push(
         ItemScenario {
-            id: ItemId::random(&second_cal),
+            url: random_url(&second_cal),
             initial_state: LocatedState::BothSynced( ItemState{
                 calendar: second_cal.clone(),
                 name: String::from("Task I"),
@@ -249,7 +250,7 @@ pub fn scenarii_basic() -> Vec<ItemScenario> {
 
     tasks.push(
         ItemScenario {
-            id: ItemId::random(&second_cal),
+            url: random_url(&second_cal),
             initial_state: LocatedState::BothSynced( ItemState{
                 calendar: second_cal.clone(),
                 name: String::from("Task J"),
@@ -263,7 +264,7 @@ pub fn scenarii_basic() -> Vec<ItemScenario> {
 
     tasks.push(
         ItemScenario {
-            id: ItemId::random(&second_cal),
+            url: random_url(&second_cal),
             initial_state: LocatedState::BothSynced( ItemState{
                 calendar: second_cal.clone(),
                 name: String::from("Task K"),
@@ -281,7 +282,7 @@ pub fn scenarii_basic() -> Vec<ItemScenario> {
 
     tasks.push(
         ItemScenario {
-            id: ItemId::random(&second_cal),
+            url: random_url(&second_cal),
             initial_state: LocatedState::BothSynced( ItemState{
                 calendar: second_cal.clone(),
                 name: String::from("Task L"),
@@ -295,7 +296,7 @@ pub fn scenarii_basic() -> Vec<ItemScenario> {
 
     tasks.push(
         ItemScenario {
-            id: ItemId::random(&second_cal),
+            url: random_url(&second_cal),
             initial_state: LocatedState::BothSynced( ItemState{
                 calendar: second_cal.clone(),
                 name: String::from("Task M"),
@@ -313,7 +314,7 @@ pub fn scenarii_basic() -> Vec<ItemScenario> {
 
     tasks.push(
         ItemScenario {
-            id: ItemId::random(&third_cal),
+            url: random_url(&third_cal),
             initial_state: LocatedState::BothSynced( ItemState{
                 calendar: third_cal.clone(),
                 name: String::from("Task N"),
@@ -331,7 +332,7 @@ pub fn scenarii_basic() -> Vec<ItemScenario> {
 
     tasks.push(
         ItemScenario {
-            id: ItemId::random(&third_cal),
+            url: random_url(&third_cal),
             initial_state: LocatedState::BothSynced( ItemState{
                 calendar: third_cal.clone(),
                 name: String::from("Task O"),
@@ -347,10 +348,10 @@ pub fn scenarii_basic() -> Vec<ItemScenario> {
         }
     );
 
-    let id_p = ItemId::random(&third_cal);
+    let url_p = random_url(&third_cal);
     tasks.push(
         ItemScenario {
-            id: id_p.clone(),
+            url: url_p.clone(),
             initial_state: LocatedState::BothSynced( ItemState{
                 calendar: third_cal.clone(),
                 name: String::from("Task P"),
@@ -369,16 +370,16 @@ pub fn scenarii_basic() -> Vec<ItemScenario> {
         }
     );
 
-    let id_q = ItemId::random(&third_cal);
+    let url_q = random_url(&third_cal);
     tasks.push(
         ItemScenario {
-            id: id_q.clone(),
+            url: url_q.clone(),
             initial_state: LocatedState::None,
             local_changes_to_apply: Vec::new(),
             remote_changes_to_apply: vec![ChangeToApply::Create(third_cal.clone(), Item::Task(
                 Task::new_with_parameters(
                     String::from("Task Q, created on the server"),
-                    id_q.to_string(), id_q,
+                    url_q.to_string(), url_q,
                     CompletionStatus::Uncompleted,
                     SyncStatus::random_synced(), Some(Utc::now()), Utc::now(), "prod_id".to_string(), Vec::new() )
             ))],
@@ -390,15 +391,15 @@ pub fn scenarii_basic() -> Vec<ItemScenario> {
         }
     );
 
-    let id_r = ItemId::random(&third_cal);
+    let url_r = random_url(&third_cal);
     tasks.push(
         ItemScenario {
-            id: id_r.clone(),
+            url: url_r.clone(),
             initial_state: LocatedState::None,
             local_changes_to_apply: vec![ChangeToApply::Create(third_cal.clone(), Item::Task(
                 Task::new_with_parameters(
                     String::from("Task R, created locally"),
-                    id_r.to_string(), id_r,
+                    url_r.to_string(), url_r,
                     CompletionStatus::Uncompleted,
                     SyncStatus::NotSynced, Some(Utc::now()), Utc::now(), "prod_id".to_string(), Vec::new() )
             ))],
@@ -423,7 +424,7 @@ pub fn scenarii_first_sync_to_local() -> Vec<ItemScenario> {
 
     tasks.push(
         ItemScenario {
-            id: ItemId::random(&cal1),
+            url: random_url(&cal1),
             initial_state: LocatedState::Remote( ItemState{
                 calendar: cal1.clone(),
                 name: String::from("Task A1"),
@@ -441,7 +442,7 @@ pub fn scenarii_first_sync_to_local() -> Vec<ItemScenario> {
 
     tasks.push(
         ItemScenario {
-            id: ItemId::random(&cal2),
+            url: random_url(&cal2),
             initial_state: LocatedState::Remote( ItemState{
                 calendar: cal2.clone(),
                 name: String::from("Task A2"),
@@ -459,7 +460,7 @@ pub fn scenarii_first_sync_to_local() -> Vec<ItemScenario> {
 
     tasks.push(
         ItemScenario {
-            id: ItemId::random(&cal1),
+            url: random_url(&cal1),
             initial_state: LocatedState::Remote( ItemState{
                 calendar: cal1.clone(),
                 name: String::from("Task B1"),
@@ -487,7 +488,7 @@ pub fn scenarii_first_sync_to_server() -> Vec<ItemScenario> {
 
     tasks.push(
         ItemScenario {
-            id: ItemId::random(&cal3),
+            url: random_url(&cal3),
             initial_state: LocatedState::Local( ItemState{
                 calendar: cal3.clone(),
                 name: String::from("Task A3"),
@@ -505,7 +506,7 @@ pub fn scenarii_first_sync_to_server() -> Vec<ItemScenario> {
 
     tasks.push(
         ItemScenario {
-            id: ItemId::random(&cal4),
+            url: random_url(&cal4),
             initial_state: LocatedState::Local( ItemState{
                 calendar: cal4.clone(),
                 name: String::from("Task A4"),
@@ -523,7 +524,7 @@ pub fn scenarii_first_sync_to_server() -> Vec<ItemScenario> {
 
     tasks.push(
         ItemScenario {
-            id: ItemId::random(&cal3),
+            url: random_url(&cal3),
             initial_state: LocatedState::Local( ItemState{
                 calendar: cal3.clone(),
                 name: String::from("Task B3"),
@@ -551,7 +552,7 @@ pub fn scenarii_transient_task() -> Vec<ItemScenario> {
 
     tasks.push(
         ItemScenario {
-            id: ItemId::random(&cal),
+            url: random_url(&cal),
             initial_state: LocatedState::Local( ItemState{
                 calendar: cal.clone(),
                 name: String::from("A task, so that the calendar actually exists"),
@@ -567,16 +568,16 @@ pub fn scenarii_transient_task() -> Vec<ItemScenario> {
         }
     );
 
-    let id_transient = ItemId::random(&cal);
+    let url_transient = random_url(&cal);
     tasks.push(
         ItemScenario {
-            id: id_transient.clone(),
+            url: url_transient.clone(),
             initial_state: LocatedState::None,
             local_changes_to_apply: vec![
                 ChangeToApply::Create(cal, Item::Task(
                     Task::new_with_parameters(
                         String::from("A transient task that will be deleted before the sync"),
-                        id_transient.to_string(), id_transient,
+                        url_transient.to_string(), url_transient,
                         CompletionStatus::Uncompleted,
                         SyncStatus::NotSynced, Some(Utc::now()), Utc::now(),
                         "prod_id".to_string(), Vec::new() )
@@ -637,8 +638,8 @@ async fn populate_test_provider(scenarii: &[ItemScenario], mock_behaviour: Arc<M
         let new_item = Item::Task(
             Task::new_with_parameters(
                 state.name.clone(),
-                item.id.to_string(),
-                item.id.clone(),
+                item.url.to_string(),
+                item.url.clone(),
                 completion_status,
                 sync_status,
                 Some(now),
@@ -676,12 +677,12 @@ async fn apply_changes_on_provider(provider: &mut Provider<Cache, CachedCalendar
 
         let mut calendar_id = initial_calendar_id.clone();
         for local_change in &item.local_changes_to_apply {
-            calendar_id = Some(apply_change(provider.local(), calendar_id, &item.id, local_change, false).await);
+            calendar_id = Some(apply_change(provider.local(), calendar_id, &item.url, local_change, false).await);
         }
 
         let mut calendar_id = initial_calendar_id;
         for remote_change in &item.remote_changes_to_apply {
-            calendar_id = Some(apply_change(provider.remote(), calendar_id, &item.id, remote_change, true).await);
+            calendar_id = Some(apply_change(provider.remote(), calendar_id, &item.url, remote_change, true).await);
         }
     }
 }
@@ -707,14 +708,14 @@ async fn get_or_insert_calendar(source: &mut Cache, id: &CalendarId)
 }
 
 /// Apply a single change on a given source, and returns the calendar ID that was modified
-async fn apply_change<S, C>(source: &S, calendar_id: Option<CalendarId>, item_id: &ItemId, change: &ChangeToApply, is_remote: bool) -> CalendarId
+async fn apply_change<S, C>(source: &S, calendar_id: Option<CalendarId>, item_url: &Url, change: &ChangeToApply, is_remote: bool) -> CalendarId
 where
     S: CalDavSource<C>,
     C: CompleteCalendar + DavCalendar, // in this test, we're using a calendar that mocks both kinds
 {
     match calendar_id {
         Some(cal) => {
-            apply_changes_on_an_existing_item(source, &cal, item_id, change, is_remote).await;
+            apply_changes_on_an_existing_item(source, &cal, item_url, change, is_remote).await;
             cal
         },
         None => {
@@ -723,14 +724,14 @@ where
     }
 }
 
-async fn apply_changes_on_an_existing_item<S, C>(source: &S, calendar_id: &CalendarId, item_id: &ItemId, change: &ChangeToApply, is_remote: bool)
+async fn apply_changes_on_an_existing_item<S, C>(source: &S, calendar_id: &CalendarId, item_url: &Url, change: &ChangeToApply, is_remote: bool)
 where
     S: CalDavSource<C>,
     C: CompleteCalendar + DavCalendar, // in this test, we're using a calendar that mocks both kinds
 {
     let cal = source.get_calendar(calendar_id).await.unwrap();
     let mut cal = cal.lock().unwrap();
-    let task = cal.get_item_by_id_mut(item_id).await.unwrap().unwrap_task_mut();
+    let task = cal.get_item_by_id_mut(item_url).await.unwrap().unwrap_task_mut();
 
     match change {
         ChangeToApply::Rename(new_name) => {
@@ -753,8 +754,8 @@ where
         },
         ChangeToApply::Remove => {
             match is_remote {
-                false => cal.mark_for_deletion(item_id).await.unwrap(),
-                true => cal.delete_item(item_id).await.unwrap(),
+                false => cal.mark_for_deletion(item_url).await.unwrap(),
+                true => cal.delete_item(item_url).await.unwrap(),
             };
         },
         ChangeToApply::Create(_calendar_id, _item) => {