Since the market is only open 6.5 hours a day, will MMs discount nearly 24 hr worth of theta in 6.5 hours? (Minus some gap risk/overnight risk premium I would assume). I hear people say this all the time... However I ran the following experiment on Google Jun15'12 570C. The currently calculated time to expiration is now exactly 2.045133 days / 365 for annualization = 0.005603. Putting this into Black Scholes I get the exact price of the option that MMs quote right now, so I'm not seeing any discounting being done? And I'm not seeing any decline in IVs either. So how does this work?