Use the three buttons on your tama: A (left), B (middle) and C (right) to set/change the time.
Press B button to bring up the time screen
Press & hold button A, then press C to start setting the date
Use A to scroll to the right date and B to confirm info
Work thru' each part of the clock until the date and time is correct (make sure that you set the time to AM - Morning or PM - Afternoon as appropriate!)