[tz+] / [tz-] Zinstage Tokens (German Tax Day Number)
The ascending Zinstage [tz+] and descending Zinstage [tz-] day tokens correspond to the ascending and descending amortization day counts found in many German diaries.
This day count differs from the normal day count by the fact that it is based on 12 months of 30 days, hence a year of 360 days.
•[tz+] equals 1 on the first day of the year, and 1 + (m-1) on the first day of month m. On months that contain 31 days, the value is the same for days 30 and 31.
•[tz-] equals 360 minus the value of [tz+].
To force the displaying of ascending and descending days over 3 digits (ie. 001, 010, 057, ...), use an uppercase "T" in the tokens [Tz+] and [Tz-].