alt-r/file/new then add the following line
on *:start:{ .timestamp -f 12[HH:nn:ss] }
example makes [12:00:00] but put what you want in there, in simple terms the problem stems from the INI file that the time stamp is saved in doesnt accept control codes, so instead you just set it here, JUST rember you set it here, else you well one day change it and wonder why it keeps reverting back.
