anyway to show 0 previous messages when entering the chatroom? or, have the chat room refreshed ans all old messages deleted after a certain time of inactivity?

also the global settings I use for the date format are not taking I have it blank but at the begininng of the chat it has xx:xx:xx as the time format. Is there a way to elimate timestamps all together or to over ride this? Ideally I would like x:xx but can get it to alter at all.

thx