Prairial

Prairial is a calendar utility that allows converting between the standard calendar (a.k.a. Greogorian) and the short-lived French Revolution one. 

The Today screen widget presents the present date of the Revolution era.

The Apple Watch companion presents the present date of the Revolution era on 2 alternate screens, one with the standard image representation of the month,  and the decimal time of the day (10 hours of 100 minutes of 100 seconds).