I am currently doing a project using Black-Scholes call option.
I had to gather a sample of data on the price of a call option for
a company starting on 1/18/2011 through 2/15/2011; I the April 15, 2011
expiration date.

What I am confused about is, when doing the calculations do I need to factor in the
days after 2/15/2011 up to the expiration date or the simply the difference between
1/18/2011 and 2/15/2011 over 252 day:

Example:
Between 1/18/2011 and 2/15/2011 is 24 days (with 1/18/2011 being an increment of 1 and 2/15/2011 of 24),.

So, do I simply do (2/15/2011-1/18/2011)/252 OR do I factor( add) in the remaining days till the option expires on April 15,2011 in the above equation.


Can someone help me with that?