There are certain things you can’t name a file in Windows 10 due to design choices from MS-DOS.
Now, he tries to soften the suck here, noting the degree to which MSFT does things like this to ensure backwards compatibility. Bollocks. There’s no reason to continue this shit, especially when it comes (as it does) at the expense of modern function and stability — or correctness.
It’s that last bit that really points out MSFT’s ridiculousness here. 30 years ago, when Excel was first introduced, there was a well-known bug in Lotus 1-2-3 (the prior spreadsheet king); Lotus treated 1900 as a leap year, which is was NOT. Even so, 2/29/1900 was a valid date.
And Microsoft broke Excel to mirror the behavior, and continues to “honor” this bullshit to this day — in fact, the bug is a part of the requirements for the Open Office standard as a result.
(Don’t @ me about leap years. No, it’s not just every 4 years. It’s ever 4 years UNLESS it’s a century year that is NOT divisible by 400. This is why, for your whole life, every-4-years works — because 2000 was an exception to an exception that only comes around every 400 years.)