fix 2-parameter case for *playback

irc/channel.go

 	// autoreplay any messages as necessary
 	var items []history.Item
 
+	hasAutoreplayTimestamps := false
 	var start, end time.Time
 	if rb.session.zncPlaybackTimes.ValidFor(channel.NameCasefolded()) {
+		hasAutoreplayTimestamps = true
 		start, end = rb.session.zncPlaybackTimes.start, rb.session.zncPlaybackTimes.end
 	} else if !rb.session.autoreplayMissedSince.IsZero() {
 		// we already checked for history caps in `playReattachMessages`
+		hasAutoreplayTimestamps = true
 		start = time.Now().UTC()
 		end = rb.session.autoreplayMissedSince
 	}
 
-	if !start.IsZero() || !end.IsZero() {
+	if hasAutoreplayTimestamps {
 		_, seq, _ := channel.server.GetHistorySequence(channel, client, "")
 		if seq != nil {
 			zncMax := channel.server.Config().History.ZNCMax

irc/znc.go

 	now := time.Now().UTC()
 	var start, end time.Time
 	switch len(params) {
+	case 2:
+		// #1205: this should have the same semantics as `LATEST *`
 	case 3:
 		// #831: this should have the same semantics as `LATEST timestamp=qux`,
 		// or equivalently `BETWEEN timestamp=$now timestamp=qux`, as opposed to