I just noticed that in OSX 10.9 Mavericks, Apple has included the Hindu Calendar as a System Calendar within the Macintosh Operating System.
English Gregorian Calendar
Hindu / Indian National Calendar
To enable the Hindu or Indian National Calendar, Navigate to Apple Menu > System Preferences > Language & Region > Under Calendar Menu, choose Indian National Calendar
That’s it. You are done. Now, you can see the Hindu Year in your active calendars with Hindu Months and Years.
Thanks & Regards
Mandar Apte