Hi Ravi,
besides changing the ressource calendar over XOG, which is indeed supported, you could also consider using an other work investment for tracking holidays and reducing capacity. You could have a company wide one or one of for each department.
An interface can easily create team entries and allocations on the other work over XOG and maybe event the REST API (not sure how far the REST Interface right now is).
One more reason for :this adding an exception to a calendar has an sometimes unwanted effect on hard allocation for the resource: the amount of hours/day for a hard booking changes (the availability has changed) outside the requisition process.
There are also some other advantages like beeing able to track the holiday time, rights management, .... but also disadvantages (line investments have to be reduced in the holiday period).
I have done both solution for customers, but for our own inhouse implementation we preffered the other work solution.
Kind regards,
Sergiu Gavrila