SemVer has two rules that the previous scheme violates:
1. major/minor/patch numbers can't start with a leading 0. Changing `%d` to `%-d` removes the leading zero. I also applied it to the year just in case :):
```
>>> print(now.strftime(f"%Y.%m.%d"))
2023.09.01
>>> print(now.strftime(f"%Y.%-m.%-d"))
2023.9.1
```
2. there can't be four dot-separated sections of the version. In this PR, I merge the year and month into one field (with a leading zero on the month!) so the seconds is the "patch" version, like this:
```
>>> print(now.strftime(f"%-Y%m.%-d.{modifier}"))
202309.1.82922
```
