3·6·9 Counter

Every digit is added left to right: month, day, year, hour, minute. Whenever the running total becomes two digits, those two digits are added together before moving on to the next digit.

03/15/1984 3:50
0+3=3 +1=4 +5=9 +1=10=1+0=1 +9=10=1+0=1 +8=9 +4=13=1+3=4 +0=4 +3=7 +5=12=1+2=3 +0=3 → 3

Each Part adds up the month, day, year, hour and minute on their own, without carrying into the next. Chaining those part numbers always lands on the same answer as the full chain.

The hour uses a 12-hour clock: 9 PM counts as 09, and noon and midnight count as 12. AM/PM isn't added. On the hour, the minute part is 0+0 = 0.

Within any hour the result climbs by one each minute, so a 3, 6 or 9 comes around every third minute.