Karmen,
From what I can find Bhadra is a month of the Hindu calendar, and in the Indian civil calendar is the sixth month beginning on the 23rd August and ending 22nd September. In the Nepali calendar, it is the fifth month.
I also found that in lunar religious calendars, the monthy may begin on either the new or full moon around that date (I think
)
So that is possibly the connection, and it could be "moveable".
By the way, Father's day in Thailand is set as the day of the Monarch's birthday. (Another useless snippet to throw into a boring conversation)
Paul.