diff --git a/application/application.go b/application/application.go
index 4338899..67ce40f 100644
--- a/application/application.go
+++ b/application/application.go
@@ -60,7 +60,7 @@ func (rai *RicochetApplicationInstance) ChatMessage(messageID uint32, when time.
 	return true
 }
 
-func (rai *RicochetApplicationInstance) ChatMessageAck(messageID uint32) {
+func (rai *RicochetApplicationInstance) ChatMessageAck(messageID uint32, accepted bool) {
 	rai.ChatMessageAckHandler(rai, messageID)
 }
 
diff --git a/channels/chatchannel.go b/channels/chatchannel.go
index c4e6e19..01ba01e 100644
--- a/channels/chatchannel.go
+++ b/channels/chatchannel.go
@@ -35,22 +35,34 @@ type ChatChannelHandler interface {
 	// the message successfully, and false to NACK and refuse the message.
 	ChatMessage(messageID uint32, when time.Time, message string) bool
 	// ChatMessageAck is called when an acknowledgement of a sent message is received.
-	ChatMessageAck(messageID uint32)
+	ChatMessageAck(messageID uint32, accepted bool)
 }
 
-// SendMessage sends a given message using this channe
-func (cc *ChatChannel) SendMessage(message string) {
+// SendMessage sends a given message using this channel, and returns the
+// messageID, which will be used in ChatMessageAck when the peer acknowledges
+// this message.
+func (cc *ChatChannel) SendMessage(message string) uint32 {
+	return cc.SendMessageWithTime(message, time.Now())
+}
+
+// SendMessageWithTime is identical to SendMessage, but also sends the provided time.Time
+// as a rough timestamp for when this message was originally sent. This should be used
+// when retrying or sending queued messages.
+func (cc *ChatChannel) SendMessageWithTime(message string, when time.Time) uint32 {
+	delta := time.Now().Sub(when) / time.Second
 	messageBuilder := new(utils.MessageBuilder)
-	//TODO Implement Chat Number
-	data := messageBuilder.ChatMessage(message, cc.lastMessageID)
+	messageID := cc.lastMessageID
 	cc.lastMessageID++
+	data := messageBuilder.ChatMessage(message, messageID, int64(delta))
 	cc.channel.SendMessage(data)
+	return messageID
 }
 
-// Acknowledge indicates the given messageID was received
-func (cc *ChatChannel) Acknowledge(messageID uint32) {
+// Acknowledge indicates that the given messageID was received, and whether
+// it was accepted.
+func (cc *ChatChannel) Acknowledge(messageID uint32, accepted bool) {
 	messageBuilder := new(utils.MessageBuilder)
-	cc.channel.SendMessage(messageBuilder.AckChatMessage(messageID))
+	cc.channel.SendMessage(messageBuilder.AckChatMessage(messageID, accepted))
 }
 
 // Type returns the type string for this channel, e.g. "im.ricochet.chat".
@@ -132,13 +144,9 @@ func (cc *ChatChannel) Packet(data []byte) {
 		if err == nil {
 			if res.GetChatMessage() != nil {
 				ack := cc.Handler.ChatMessage(res.GetChatMessage().GetMessageId(), time.Now(), res.GetChatMessage().GetMessageText())
-				if ack {
-					cc.Acknowledge(res.GetChatMessage().GetMessageId())
-				} else {
-					//XXX
-				}
-			} else if res.GetChatAcknowledge() != nil {
-				cc.Handler.ChatMessageAck(res.GetChatMessage().GetMessageId())
+				cc.Acknowledge(res.GetChatMessage().GetMessageId(), ack)
+			} else if ack := res.GetChatAcknowledge(); ack != nil {
+				cc.Handler.ChatMessageAck(ack.GetMessageId(), ack.GetAccepted())
 			}
 			// XXX?
 		}
diff --git a/channels/chatchannel_test.go b/channels/chatchannel_test.go
index b404258..8ea0b12 100644
--- a/channels/chatchannel_test.go
+++ b/channels/chatchannel_test.go
@@ -76,7 +76,7 @@ func (tcch *TestChatChannelHandler) ChatMessage(messageID uint32, when time.Time
 	return true
 }
 
-func (tcch *TestChatChannelHandler) ChatMessageAck(messageID uint32) {
+func (tcch *TestChatChannelHandler) ChatMessageAck(messageID uint32, accepted bool) {
 
 }
 
@@ -116,7 +116,7 @@ func TestChatChannelOperations(t *testing.T) {
 		t.Errorf("After Successful Result ChatChannel Is Still Pending")
 	}
 
-	chat := messageBuilder.ChatMessage("message text", 0)
+	chat := messageBuilder.ChatMessage("message text", 0, 0)
 	chatChannel.Packet(chat)
 
 	chatChannel.SendMessage("hello")
diff --git a/examples/echobot/main.go b/examples/echobot/main.go
index c20bdc5..6fd3a77 100644
--- a/examples/echobot/main.go
+++ b/examples/echobot/main.go
@@ -32,7 +32,7 @@ func (echobot *RicochetEchoBot) ChatMessage(messageID uint32, when time.Time, me
 	return true
 }
 
-func (echobot *RicochetEchoBot) ChatMessageAck(messageID uint32) {
+func (echobot *RicochetEchoBot) ChatMessageAck(messageID uint32, accepted bool) {
 
 }
 
diff --git a/utils/messagebuilder.go b/utils/messagebuilder.go
index bd5616f..9b932f1 100644
--- a/utils/messagebuilder.go
+++ b/utils/messagebuilder.go
@@ -195,10 +195,11 @@ func (mb *MessageBuilder) AuthResult(accepted bool, isKnownContact bool) []byte
 }
 
 // ChatMessage constructs a chat message with the given content.
-func (mb *MessageBuilder) ChatMessage(message string, messageID uint32) []byte {
+func (mb *MessageBuilder) ChatMessage(message string, messageID uint32, timeDelta int64) []byte {
 	cm := &Protocol_Data_Chat.ChatMessage{
 		MessageId:   proto.Uint32(messageID),
 		MessageText: proto.String(message),
+		TimeDelta:   proto.Int64(timeDelta),
 	}
 	chatPacket := &Protocol_Data_Chat.Packet{
 		ChatMessage: cm,
@@ -209,10 +210,10 @@ func (mb *MessageBuilder) ChatMessage(message string, messageID uint32) []byte {
 }
 
 // AckChatMessage constructs a chat message acknowledgement.
-func (mb *MessageBuilder) AckChatMessage(messageID uint32) []byte {
+func (mb *MessageBuilder) AckChatMessage(messageID uint32, accepted bool) []byte {
 	cr := &Protocol_Data_Chat.ChatAcknowledge{
 		MessageId: proto.Uint32(messageID),
-		Accepted:  proto.Bool(true),
+		Accepted:  proto.Bool(accepted),
 	}
 	pc := &Protocol_Data_Chat.Packet{
 		ChatAcknowledge: cr,
diff --git a/utils/messagebuilder_test.go b/utils/messagebuilder_test.go
index cdd9f27..3f1c16a 100644
--- a/utils/messagebuilder_test.go
+++ b/utils/messagebuilder_test.go
@@ -26,7 +26,7 @@ func TestOpenAuthenticationChannel(t *testing.T) {
 
 func TestChatMessage(t *testing.T) {
 	messageBuilder := new(MessageBuilder)
-	messageBuilder.ChatMessage("Hello World", 0)
+	messageBuilder.ChatMessage("Hello World", 0, 0)
 	// TODO: More Indepth Test Of Output
 }