[yuliyp]

It requires someone to at some point remember that "Hey when I was a kid 20 years ago the solstice was on December 22 but now it's on December 17, what happened?" and then go looking at historical records to generate a trend line with a slope of 0.25 days / year. The measurement doesn't have to be at one point.

[amluto]

Sure, but it needs an extra digit or two do do as well as the Gregorian calendar. Doable, but longer records are needed.

[yuliyp]

The adjustment to 365.25 came during Roman times. The Gregorian adjustment came after well over a thousand years to realize the drift since Julius Caesar's time.