Here is the example of custom clock in which you can calculate seconds, minutes etc
10 REM “CLOCK”
20 IF SYS_TIME <> TIME THEN GOTO 30 ELSE GOTO 80
30 SECONDS = SECONDS + 1
40 IF SECONDS >= 59 THEN MINUTES = MINUTES + 1 , SECONDS = 0
50 IF MINUTES = 59 THEN HOURS = HOURS + 1 , MINUTES = 0
60 IF HOURS = 23 THEN DAYS = DAYS + 1 , HOURS = 0
70 IF DAYS > 30 THEN DAYS = 0
80 SYS_TIME = TIME