What versioning system do you use or have seen in practice?

In a company I'm working at, I'm seeing something like A.B.YYWW.RR - A : Major Hardware Revision - B : Minor Hardware Revision - YY : 20YY year code (e.g. 2021 would yeld YY=21) - WW : ISO week (https://en.wikipedia.org/wiki/ISO_week_date) - RR : Firmware Revision What other versioning system have you seen in the field? --------- Also does versioning have to necessarily be incremental? What if the last few digits are a portion of a git hash (At least for internal or test releases). One other possibility is to use iso week date plus revision number (YYYY.WW.R) e.g. `2020.11.7`