Prairial by Laurent Rodier is a Windows 8/RT app that converts between the French Republican and Gregorian calendars. It displays the usual calendar girls for each month, and can display an entire month on one screen. It has live tile support, so it shows the date on your Windows Start screen. It also converts between standard and decimal times. It appears to display the current decimal time on a basic analog clock with 10 at the top. Since I don't have Windows 8 or RT, I have not tried it, but it's available for $1.49 in the Windows Market. It just happens that Prairial is the current month, the last month of spring.
Duodi 22 Prairial an CCXXI à 1 heure 24 minutes décimales t.m.P.