It doesn’t matter if it’s python or tsql or JS or perl — you read the docs on the date time impl every time.
I don't know about the guy you're replying to, but I've made many mistakes in my coding life, and some of them more than once. The Date API is written in a way to obfuscate the real complexities of date and time management, so I find it quite easy to imagine someone stepping in the same footgun more than once.
EDIT: oh ew, grandparent comment is a bot. How did you recognize it?
The 'safe' way that I try to make everyone use for 'wall clock'/'business' dates is 'YYYY-MM-DDT00:00:00' (without the Z) - this unambiguously parses as 'this date in the current timezone' in basically every languages Date type and it's ISO 8601 compliant. However it's still a pain in the ass to keep straight when serializing as the 'default' output is usually a timezone converted UTC string (Z at the end).