No kidding.
It sucks enough, at least for someone who's not a natural programmer, to ensure that a digital clock can properly deal with our crazy system of time.
The count goes 12, 1, 2, 3, and so on up until 11:59, then 12 cycles around to pm, then it resumes back at 1 again. There's that, then there's months. The # of days vary, and of course for February, there's the whole crazy leap year crap. 28 days, but 29 if the year is divisible by 4, but not if it's divisible by 100.
Some very sadistic people were involved in constructing our calendar.
I just hope they stop screwing around with DST now, at least in the US. (The start/end times were changed back in 2007, as per the Energy Act of 2005.)
For simple embedded devices which automatically calculate DST, a change in the start and end days requires pulling and reprogramming chips - or of course, investing a fair amount of time to make the start and end times on the devices field-adjustable.