Auto-substitution Dates and Times: Language Long and Short what are differences


I am trying to find out what each drop down option is for the various languages (I work with 11) long/short date and time are.

I can guess that HH is 24 hour and H is 12.  However, many of the languages have something unique.  German with their long/short time there is Uhr'.  Japanese Long date has 2020年1月22日.  Korean has a "tt" option in their long/short time.

I have not been able to find anywhere exactly what the distinction is with all these different options.  Does anyone have any information on these differences and what each unique, I think Regex, character does?