Option pricing calculation does not consider number of trading day/ holiday between today and expiry date.. It consider CALENDER DAYS so april expiry is 41 days away from today, so the theoratical price of option say 2700 CAll option should be the sum of
1) Intrinsic value today i.e. spot price - strike price for call option
2) Time value for 41 days = which roughly comes to about 158 Rs.
when 35 days are left for april expiry = the time value will be approx 145 Rs.
That means, irrespective of what happens to other variables, this option will loose 13 Rs of value in next 5 days. If Nifty moves up, so part 1 of the option premium will increase.
Happy trading.