[missthethunder]

“The calendar in Microsoft Excel incorrectly
has the year 1900 as a leap year.”

The calendar on my phone does not
show 1900 as a leap year.

But it shows 1896 and 1904,
as leap years.

Weird

[Romulus]

That would be correct.

[HartleyMBaldwin]

Only every fourth even-hundred year is a leap year. Thus 1900 wasn’t a leap year, 2000 was, 2100, 2200, and 2300 won’t be, and 2400 will be.

[Campion]

Yes, that’s the difference between the Gregorian and Julian calendars. The Julian calendar gives you a leap year every four years, resulting in a year that’s exactly 365.25 days long. But the real astronomical year is about 13 minutes shorter than that, so the Gregorian calendar skips a leap year on years divisible by 100, unless they’re also divisible by 400. 2000 (divisible by 400) was a leap year, 1900 (not divisible by 400) was not.

[reviled downesdad]

Millenial years are supposed to be skipped for leap years
Per the original Gregorian calendar

[Theophilus]

Every turn of a century is not a leap year (it skips) unless it also the turn of a millennium (it does not skip), like 2000.