100 x 365 x 24 x 60 x 60 x 1000
= 36500 x 24 x 60 x 60 x 1000
= 876000 x 60 x 60 x 1000
= 52560000 x 60 x 1000
= 3153600000 x 1000
= 3153600000000 milliseconds
1 millisecond = 1/1000 second.
60 second per minute
60 minutes per hour
24 hours per day
365 days per year, but 364 days every 4 years.
25 "leap years" per century