If you'd gone to bed last night a little over 260 years ago it would've been September 2nd. Then, at dawn this morning, it's suddenly the 14th September and you're 12 days older than you were the night before!
Except you aren't, of course: not really. Only the names (in this case, the numbers) have been changed.
And changed in order to synchronise our human written calendar better with the only one that really matters - the calendar of the skies and the sun and moon and seasons.
Even that isn't 'right' of course, given that the earth inconveniently takes 365-and-a-quarter days to orbit the sun (which is why we need a leap year every so often).
All of which brings home how artificial this human construct, 'time', is.
Tell that to the boss next time you're late!