My theory is related to the Y2K crisis
My theory is that it wasn't very common to shorten the years in the 1800's, 1700, 1600; but that using the apostrophe for the year of dates became common after 1931, when two-digit years wouldn't be confused with days, and when writing was moving towards efficiency, and was then followed by the digital data entry period. Incidentally I see that Google isn't Y2K compliant or consistent in how they write dates.
I have tried to look a old documents and registries, but I need to do some deeper digging. Thanks