diff --git a/sable_network/src/network/network/account_state.rs b/sable_network/src/network/network/account_state.rs
index 5d06f7b..6acd79a 100644
--- a/sable_network/src/network/network/account_state.rs
+++ b/sable_network/src/network/network/account_state.rs
@@ -115,6 +115,7 @@ impl Network {
 
         self.historic_users.update_account(
             user,
+            event.timestamp,
             new_account
                 .as_ref()
                 .and_then(|id| accounts.get(id).map(|a| a.name)),
diff --git a/sable_network/src/network/network/user_history.rs b/sable_network/src/network/network/user_history.rs
index 0a8814c..d4c6626 100644
--- a/sable_network/src/network/network/user_history.rs
+++ b/sable_network/src/network/network/user_history.rs
@@ -17,9 +17,26 @@ impl HistoricUserStore {
 
     /// Add a user to the store.
     ///
-    /// This should be called by the [`Network`] for every change to a client-protocol-visible attribute
-    /// of the user object.
-    pub fn add(&mut self, user: &mut state::User, nickname: Nickname, account: Option<Nickname>) {
+    /// This (or one of the update variants) should be called by the [`Network`] for every change
+    /// to a client-protocol-visible attribute of the user object.
+    ///
+    /// The provided timestamp will be applied to the previous historic user corresponding to this
+    /// user object, to indicate when it ceased to be relevant, and the user object's serial number
+    /// will be incremented.
+    pub fn add(
+        &mut self,
+        user: &mut state::User,
+        timestamp: i64,
+        nickname: Nickname,
+        account: Option<Nickname>,
+    ) {
+        if let Some(existing) = self
+            .users
+            .get_mut(&HistoricUserId::new(user.id, user.serial))
+        {
+            existing.timestamp = Some(timestamp);
+        }
+
         user.serial += 1;
 
         let historic_user = HistoricUser {
@@ -31,6 +48,7 @@ impl HistoricUserStore {
             realname: user.realname,
             away_reason: user.away_reason,
             account,
+            timestamp: None,
         };
 
         let new_id = HistoricUserId::new(user.id, user.serial);
@@ -39,7 +57,7 @@ impl HistoricUserStore {
     }
 
     /// Update the details of a user that's already in the store, reusing the existing nickname and account
-    pub fn update(&mut self, user: &mut state::User) -> HistoricUserId {
+    pub fn update(&mut self, user: &mut state::User, timestamp: i64) -> HistoricUserId {
         let old_id = HistoricUserId::new(user.id, user.serial);
 
         let Some(existing) = self.get_user(&user) else {
@@ -49,12 +67,17 @@ impl HistoricUserStore {
         let nickname = existing.nickname;
         let account = existing.account;
 
-        self.add(user, nickname, account);
+        self.add(user, timestamp, nickname, account);
         old_id
     }
 
     /// Update the details of a user that's already in the store, reusing the existing account
-    pub fn update_nick(&mut self, user: &mut state::User, nickname: Nickname) -> HistoricUserId {
+    pub fn update_nick(
+        &mut self,
+        user: &mut state::User,
+        timestamp: i64,
+        nickname: Nickname,
+    ) -> HistoricUserId {
         let old_id = HistoricUserId::new(user.id, user.serial);
 
         let Some(existing) = self.get_user(&user) else {
@@ -63,7 +86,7 @@ impl HistoricUserStore {
 
         let account = existing.account;
 
-        self.add(user, nickname, account);
+        self.add(user, timestamp, nickname, account);
         old_id
     }
 
@@ -71,6 +94,7 @@ impl HistoricUserStore {
     pub fn update_account(
         &mut self,
         user: &mut state::User,
+        timestamp: i64,
         account: Option<Nickname>,
     ) -> HistoricUserId {
         let old_id = HistoricUserId::new(user.id, user.serial);
@@ -81,7 +105,7 @@ impl HistoricUserStore {
 
         let nickname = existing.nickname;
 
-        self.add(user, nickname, account);
+        self.add(user, timestamp, nickname, account);
         old_id
     }
 
diff --git a/sable_network/src/network/network/user_state.rs b/sable_network/src/network/network/user_state.rs
index 2ecabc3..461ee33 100644
--- a/sable_network/src/network/network/user_state.rs
+++ b/sable_network/src/network/network/user_state.rs
@@ -100,7 +100,9 @@ impl Network {
                 let new_binding =
                     state::NickBinding::new(new_nick, user_id, trigger.timestamp, trigger.id);
 
-                let prev_historic_id = self.historic_users.update_nick(user, new_nick);
+                let prev_historic_id =
+                    self.historic_users
+                        .update_nick(user, trigger.timestamp, new_nick);
 
                 // Let translate_historic_user do the work of mapping the account name, then manually fill in
                 // the old (collided) nick
@@ -154,7 +156,9 @@ impl Network {
             let new_nick = new_binding.nick;
             self.nick_bindings.insert(new_nick, new_binding);
 
-            let prev_historic_id = self.historic_users.update_nick(user_object, new_nick);
+            let prev_historic_id =
+                self.historic_users
+                    .update_nick(user_object, event.timestamp, new_nick);
 
             // Emit UserNickChange update if a nick change happens as a result of this rebinding.
             if old_nick.value() != new_nick.value() {
@@ -209,6 +213,7 @@ impl Network {
         // get_mut later on
         self.historic_users.add(
             &mut user,
+            event.timestamp,
             detail.nickname,
             detail
                 .account
@@ -259,7 +264,7 @@ impl Network {
             let mut old_reason = new_reason;
             std::mem::swap(&mut user.away_reason, &mut old_reason);
 
-            self.historic_users.update(user);
+            self.historic_users.update(user, event.timestamp);
 
             let update_user = user.clone();
 
diff --git a/sable_network/src/network/state/historic.rs b/sable_network/src/network/state/historic.rs
index a9d2628..84d5734 100644
--- a/sable_network/src/network/state/historic.rs
+++ b/sable_network/src/network/state/historic.rs
@@ -11,6 +11,10 @@ pub struct HistoricUser {
     pub realname: Realname,
     pub away_reason: Option<AwayReason>,
     pub account: Option<Nickname>,
+
+    /// The time until which this historic user state was accurate - if None
+    /// then this data is current.
+    pub timestamp: Option<i64>,
 }
 
 impl wrapper::WrappedUser for HistoricUser {
@@ -70,6 +74,7 @@ impl HistoricUser {
             visible_host: user.visible_host,
             realname: user.realname,
             away_reason: user.away_reason,
+            timestamp: None,
         }
     }
 }