When i first learned of the 2038 problem, i changed the date on my computer and watched it tick up to 2^32. All sorts of things crashed, most notably, the Norton antivirus software. This was on a windows XP if I recall correctly
I vaguely remember a few different timestamp formats in use in different places, but the 100ns-tick is very common in Microsoft APIs.
FILETIME is a nominally unsigned 64-bt value. 1601-01-01 + 2^64 * 100ns = 60056-05-28. That is, Sunday May 28, 60056.