After probation, any specific days given to company to give reply on confirmation.

There is no such law.

It depends on individual terms and conditions stated in appoinment order.  During probation period only, employer should be  given notice.  If not, it is deemed that employee is confirmed from the date of such completiton of probation, whether order was given or not.

Look into the private agreement/contract/offer-appointment letter/service rules/policies drafted by employer and their published versions…..

Ideally employer, bosses should act well in advance  to set in motion appraisal if any, and communicate on cut off date of probation period regarding confirmation of service/extension of probation period if any…..