If you were born exactly on 12:00 midnight on December 31st

January 1st, which year would you say you were born in?

by right, using a 24hr clock,

12midnite of Dec31 is equal to 00:00 on 1st January.

wrong
the last possible time is 11.59.59 sec

the time u mention is 1 sec after ther 30th dec