The formula (year - 2000) * 10000 + month * 100 + day can perfectly accommodate any future dates, until we change our calendar.
however if we invent time travel, and go back into the year 2000 we wouldn't be able to store any event data. furthermore, to get back, if that data field was used to store event data and the coordinates to get back to the current location of earth, could send you to a divide by zero coordinate and you wouldn't be able to get back. The solution is to just ban time travel to the year 2000 until a patch comes out
But without zero-padding, it will sort wrong when using lexiographic order (as is common). 1180101 would sort before 171204 in many contexts, even though it should clearly come behind the latter.
I don't know, but it is possible that the GW encodes something that increases once a century or faster. There is definitely more information in two letters than two digits.