Theta Decay in Nifty Weekly Expiry

Weekly expiry compresses time. Theta (time decay) is gentle on day 1-3, then accelerates exponentially in the last 48 hours. A Nifty ATM option can lose 30-40% of premium to theta alone in the final day. Implication: buyers must be right FAST; sellers collect decaying premium. AI feature theta_decay_rate = premium lost per day / total premium, computed daily. Near expiry, high theta + low Gamma edge favours defined-risk spreads over naked buys. The model uses theta_decay_rate to size: high decay + low conviction = smaller position. This is why 'buy options every expiry' bleeds accounts -- they fight math.