diff --git a/irc/channel.go b/irc/channel.go
index 8693e037..b9af37fe 100644
--- a/irc/channel.go
+++ b/irc/channel.go
@@ -30,6 +30,7 @@ type Channel struct {
 	key               string
 	members           MemberSet
 	membersCache      []*Client // allow iteration over channel members without holding the lock
+	memberJoinTimes   map[*Client]time.Time
 	name              string
 	nameCasefolded    string
 	server            *Server
@@ -57,11 +58,12 @@ func NewChannel(s *Server, name, casefoldedName string, registered bool) *Channe
 	config := s.Config()
 
 	channel := &Channel{
-		createdTime:    time.Now().UTC(), // may be overwritten by applyRegInfo
-		members:        make(MemberSet),
-		name:           name,
-		nameCasefolded: casefoldedName,
-		server:         s,
+		createdTime:     time.Now().UTC(), // may be overwritten by applyRegInfo
+		members:         make(MemberSet),
+		memberJoinTimes: make(map[*Client]time.Time),
+		name:            name,
+		nameCasefolded:  casefoldedName,
+		server:          s,
 	}
 
 	channel.initializeLists()
@@ -550,6 +552,16 @@ func (channel *Channel) ClientModeStrings(client *Client) []string {
 	}
 }
 
+func (channel *Channel) ClientJoinTime(client *Client) *time.Time {
+	channel.stateMutex.RLock()
+	defer channel.stateMutex.RUnlock()
+	time, present := channel.memberJoinTimes[client]
+	if present {
+		return &time
+	}
+	return nil
+}
+
 func (channel *Channel) ClientHasPrivsOver(client *Client, target *Client) bool {
 	channel.stateMutex.RLock()
 	founder := channel.registeredFounder
@@ -726,6 +738,7 @@ func (channel *Channel) Join(client *Client, key string, isSajoin bool, rb *Resp
 			defer channel.stateMutex.Unlock()
 
 			channel.members.Add(client)
+			channel.memberJoinTimes[client] = time.Now()
 			firstJoin := len(channel.members) == 1
 			newChannel := firstJoin && channel.registeredFounder == ""
 			if newChannel {
@@ -1364,6 +1377,7 @@ func (channel *Channel) Quit(client *Client) {
 
 		channel.stateMutex.Lock()
 		channel.members.Remove(client)
+		delete(channel.memberJoinTimes, client)
 		channelEmpty := len(channel.members) == 0
 		channel.stateMutex.Unlock()
 		channel.regenerateMembersCache()
diff --git a/irc/handlers.go b/irc/handlers.go
index 880f6d5f..d6deaa35 100644
--- a/irc/handlers.go
+++ b/irc/handlers.go
@@ -939,7 +939,13 @@ func extjwtHandler(server *Server, client *Client, msg ircmsg.IrcMessage, rb *Re
 		claims["joined"] = 0
 		claims["cmodes"] = []string{}
 		if channel.hasClient(client) {
-			claims["joined"] = time.Now().Unix() - 100 //TODO(dan): um we need to store when clients joined for reals
+			joinTime := channel.ClientJoinTime(client)
+			if joinTime == nil {
+				// shouldn't happen, only in races
+				rb.Add(nil, server.name, "FAIL", "EXTJWT", "UNKNOWN_ERROR", client.t("Channel join time is inconsistent, JWT not generated"))
+				return false
+			}
+			claims["joined"] = joinTime.Unix()
 			claims["cmodes"] = channel.ClientModeStrings(client)
 		}
 	}