on *:join:#yourchan: {
  if ($nick(#,0) >= $+(%,peak.,$chan)) {
    set $+(%,peak.,$chan) $nick(#,0) $ctime

on *:text:!peak:#yourchan: {
  msg $chan On $date($gettok($+(%,peak.,$chan),2,32),mmm dd yyyy) $+ , there were $gettok($+(%,peak.,$chan),1,32) users in $chan $+ !

Note that you can add in the time as well as the date by just editing the output line's $date statement. That's why I used $ctime when setting the variable.

This will work for multiple channels as long as the channel names are different (i.e. not the same name on two different networks).

Invision Support
#Invision on