@itaiferber
Let us agree that:
gregorian.nextDateOf(2011-12-29) = 2011-12-30
gregorianInSamoa.nextDateOf(2011-12-29) = 2011-12-31
which means gregorian is the Gregorian calendar as it is known in the world, ignoring any local exceptions (which we specify explicitly if they are applicable).
I claim that:
gregorian.nextDateOf(2024-12-02) = 2024-12-03
gregorian.nextDateOf(2011-12-29) = 2011-12-30
In your point (3) above you say that the answer depends on DST, timezone, locate, other. Is there such a combination which gives another answer for the first? For the second you said in Samoa, but if gregorian is defined as the globally known Gregorian, is there any other combination which gives another answer? Same for other dates.