You can say Feb 29 + 365 days = Feb 28. (And Feb 29 + 730 days = Feb 27.)
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EDIT:
Note that in the context of birthdays, people use "calendar years," not "unit of time which is ~1 revolution around the sun."
Birthdays aren't celebrated every X million seconds after the moment of birth.
They are celebrated the same day each calendar year -- notwithstanding the fuzzy concept of "same day" for incongruent calendar years. There's no singuar right answer, but that is the core question: "what is the same day next (calendar) year?"
When I wrote "+ 1 year" I meant year to represent 365 or 365.25 days, not "the same day next year.":
>>> from datetime import date, timedelta
>>> year = timedelta(days=365.25)
>>> date(2024, 2, 29) + year
datetime.date(2025, 2, 28)
You may have interpreted it as begging the question, but it was not my intent—though I admit my formulation was ambiguous.
> Note that in the context of birthdays, people use "calendar years," not "unit of time which is ~1 revolution around the sun."
You've never heard someone say they've celebrated another trip around the Sun? I literally have a photo from 2007 of my daughter in Montessori celebrating her birthday by holding a globe and walking around a candle representing the Sun. I think most people probably don't really think about whether it's a calendar year or astronomical year because for most people, they are usually equivalent and it doesn't matter.
But that's all beside the point. All I meant to point out is that I disagree that March is more logical. I don't think logic points us to one month or the other. You may feel March is more logical, but I don't accept your priors, so for me March is not more logical than February.
> Birthdays aren't celebrated every X million seconds after the moment of birth.
As a surprise for a friend of mine, I threw him a gigasecond party on the day he turned 1000 million seconds old. Yes he was surprised, and a good time was had by all.
Many people say: Happy turn around the sun! and 365 is not the length of a year is the length of some years so, who knows... I'm against time zones and pro 28 days months and a couple of free days :D
"Feb 29 + 1 year" is verbatim restatement.
---
You can say Feb 29 + 365 days = Feb 28. (And Feb 29 + 730 days = Feb 27.)
---
EDIT:
Note that in the context of birthdays, people use "calendar years," not "unit of time which is ~1 revolution around the sun."
Birthdays aren't celebrated every X million seconds after the moment of birth.
They are celebrated the same day each calendar year -- notwithstanding the fuzzy concept of "same day" for incongruent calendar years. There's no singuar right answer, but that is the core question: "what is the same day next (calendar) year?"
[1] https://en.wikipedia.org/wiki/Begging_the_question