diff --git a/docs/src/tasks.md b/docs/src/tasks.md
index eb6756e22..b3285af88 100644
--- a/docs/src/tasks.md
+++ b/docs/src/tasks.md
@@ -17,6 +17,12 @@ The result of this reconciliation will be `oldtag,newtag2`, while the user almos
 
 The key names given below avoid this issue, allowing user updates such as adding a tag or deleting a dependency to be represented in a single `Update` operation.
 
+## Validity
+
+_Any_ key/value map is a valid task.
+Consumers of task data must make a best effort to interpret any map, even if it contains apparently contradictory information.
+For example, a task with status "completed" but no "end" key present should be interpreted as completed at an unknown time.
+
 ## Representations
 
 Integers are stored in decimal notation.
@@ -31,6 +37,7 @@ The following keys, and key formats, are defined:
 * `description` - the one-line summary of the task
 * `modified` - the time of the last modification of this task
 * `start` - the most recent time at which this task was started (a task with no `start` key is not active)
+* `end` - if present, the time at which this task was completed or deleted (note that this key may not agree with `status`: it may be present for a pending task, or absent for a deleted or completed task)
 * `tag_<tag>` - indicates this task has tag `<tag>` (value is an empty string)
 * `wait` - indicates the time before which this task should be hidden, as it is not actionable
 * `annotation_<timestamp>` - value is an annotation created at the given time
diff --git a/taskchampion/src/replica.rs b/taskchampion/src/replica.rs
index 2b833a323..af94f72ba 100644
--- a/taskchampion/src/replica.rs
+++ b/taskchampion/src/replica.rs
@@ -228,7 +228,7 @@ mod tests {
                 ..
             } = op
             {
-                if property == "modified" {
+                if property == "modified" || property == "end" {
                     if value.is_some() {
                         value = Some("just-now".into());
                     }
@@ -291,6 +291,13 @@ mod tests {
                     value: Some("past tense".into()),
                     timestamp: now,
                 },
+                ReplicaOp::Update {
+                    uuid: t.get_uuid(),
+                    property: "end".into(),
+                    old_value: None,
+                    value: Some("just-now".into()),
+                    timestamp: now,
+                },
                 ReplicaOp::Update {
                     uuid: t.get_uuid(),
                     property: "status".into(),
diff --git a/taskchampion/src/task/task.rs b/taskchampion/src/task/task.rs
index 40a85ba87..e151f88d5 100644
--- a/taskchampion/src/task/task.rs
+++ b/taskchampion/src/task/task.rs
@@ -57,6 +57,7 @@ enum Prop {
     Start,
     Status,
     Wait,
+    End,
 }
 
 #[allow(clippy::ptr_arg)]
@@ -263,9 +264,23 @@ impl<'r> TaskMut<'r> {
     /// Set the task's status.  This also adds the task to the working set if the
     /// new status puts it in that set.
     pub fn set_status(&mut self, status: Status) -> anyhow::Result<()> {
-        if status == Status::Pending {
-            let uuid = self.uuid;
-            self.replica.add_to_working_set(uuid)?;
+        if status == Status::Pending {}
+        match status {
+            Status::Pending => {
+                // clear "end" when a task becomes "pending"
+                if self.taskmap.contains_key(Prop::End.as_ref()) {
+                    self.set_timestamp(Prop::End.as_ref(), None)?;
+                }
+                let uuid = self.uuid;
+                self.replica.add_to_working_set(uuid)?;
+            }
+            Status::Completed | Status::Deleted => {
+                // set "end" when a task is deleted or completed
+                if !self.taskmap.contains_key(Prop::End.as_ref()) {
+                    self.set_timestamp(Prop::End.as_ref(), Some(Utc::now()))?;
+                }
+            }
+            _ => {}
         }
         self.set_string(
             Prop::Status.as_ref(),
@@ -304,6 +319,14 @@ impl<'r> TaskMut<'r> {
         self.set_status(Status::Completed)
     }
 
+    /// Mark this task as deleted.
+    ///
+    /// Note that this does not delete the task.  It merely marks the task as
+    /// deleted.
+    pub fn delete(&mut self) -> anyhow::Result<()> {
+        self.set_status(Status::Deleted)
+    }
+
     /// Add a tag to this task.  Does nothing if the tag is already present.
     pub fn add_tag(&mut self, tag: &Tag) -> anyhow::Result<()> {
         if tag.is_synthetic() {
@@ -676,6 +699,41 @@ mod test {
         });
     }
 
+    #[test]
+    fn test_set_status_pending() {
+        with_mut_task(|mut task| {
+            task.done().unwrap();
+
+            task.set_status(Status::Pending).unwrap();
+            assert_eq!(task.get_status(), Status::Pending);
+            assert!(!task.taskmap.contains_key("end"));
+            assert!(task.has_tag(&stag(SyntheticTag::Pending)));
+            assert!(!task.has_tag(&stag(SyntheticTag::Completed)));
+        });
+    }
+
+    #[test]
+    fn test_set_status_completed() {
+        with_mut_task(|mut task| {
+            task.set_status(Status::Completed).unwrap();
+            assert_eq!(task.get_status(), Status::Completed);
+            assert!(task.taskmap.contains_key("end"));
+            assert!(!task.has_tag(&stag(SyntheticTag::Pending)));
+            assert!(task.has_tag(&stag(SyntheticTag::Completed)));
+        });
+    }
+
+    #[test]
+    fn test_set_status_deleted() {
+        with_mut_task(|mut task| {
+            task.set_status(Status::Deleted).unwrap();
+            assert_eq!(task.get_status(), Status::Deleted);
+            assert!(task.taskmap.contains_key("end"));
+            assert!(!task.has_tag(&stag(SyntheticTag::Pending)));
+            assert!(!task.has_tag(&stag(SyntheticTag::Completed)));
+        });
+    }
+
     #[test]
     fn test_start() {
         with_mut_task(|mut task| {
@@ -718,6 +776,7 @@ mod test {
         with_mut_task(|mut task| {
             task.done().unwrap();
             assert_eq!(task.get_status(), Status::Completed);
+            assert!(task.taskmap.contains_key("end"));
             assert!(task.has_tag(&stag(SyntheticTag::Completed)));
 
             // redundant call does nothing..
@@ -727,6 +786,21 @@ mod test {
         });
     }
 
+    #[test]
+    fn test_delete() {
+        with_mut_task(|mut task| {
+            task.delete().unwrap();
+            assert_eq!(task.get_status(), Status::Deleted);
+            assert!(task.taskmap.contains_key("end"));
+            assert!(!task.has_tag(&stag(SyntheticTag::Completed)));
+
+            // redundant call does nothing..
+            task.delete().unwrap();
+            assert_eq!(task.get_status(), Status::Deleted);
+            assert!(!task.has_tag(&stag(SyntheticTag::Completed)));
+        });
+    }
+
     #[test]
     fn test_add_tags() {
         with_mut_task(|mut task| {