[EntropicBrew]

This is fascinating. Even sillier example, https://www.wolframalpha.com/input?i=2019-01-31+to+2016-04-0... and https://www.wolframalpha.com/input?i=2019-01-30+to+2016-04-0...

both show an identical duration of 2 years 9 months 26 days (edit: despite reporting 1032 and 1031 days respectively).

[pizzafeelsright]

Counting months and days are two very different metrics.

Months are lunar. Days are solar.

[EntropicBrew]

Depends on the calendar system, as far as this discussion goes, the Greogorian calendar system is solar even for months.