I definitely do for quick scripts, but I try to break this habit. The biggest advantage of def main() is that variables are local and not accessible to other functions defined in the same script, which can sometimes help catch bugs or typos.
sqlite is technically just one C source file, so that’s definitely a script.
The proposed time zone is to drift about 1 second every 50 years. I also suspect it wouldn’t really be a time zone in the same sense as the time zones we know - it would just be a standardised calibration reference. Dates and times expressed in “moon time” would probably just be some leap second off of a known Earth time zone, and because it’s mere seconds over centuries, I think the only use of this time zone is to calculate ultra-precise time diffs between two earth datetimes when the observer is on the moon. At least, that’s how I interpret the articles I can find about it.
there’s a pretty wild range there from fairly easy to make in a few hours to massive community effort over several decades