Tm 2001 Radio-cass

[iluvcarina]

I have recently fitted a nearly new TM 2001 radio in my car which works perfectly well, but there is a button near the top left corner with what seems to be a clock face on it, when i press it the letters adj appear but i get no reaction from any other buttons i press,i have no manual but is it simply a clock to ba set into the unit ? if so how do i set it or is it something else ?