to the computer programmers/ coders et. al. here on AnonUp.
(i am not a programmer-forgive my plebian take)
the time element in your lines of code, be it counting up or down,
in this case counting up for example. for simplcity HH:MM:SS.

when counter registers HH:MM:59
the next count should be HH: MM=1:00 not HH:MM:60
likewise... HH:59:59 next should be HH+1:00:00
and 23:59:59 next should be 00:00:00 ... not 24:60:60
follow same logic for month and year...

our world runs on codes written (hopefully) decent folks. most of the time. and sometimes we get some Kevin M. acolyte(s)

bear with me here....

this friday when all are enjoying fun beverage with our love ones...
the machines are oblivious to such things and dutifully follows the codes written for them..

just a noob question here...
when does a machine observe Zero Day?