Time to expiration T
Time to Expiration · Time decay
T is measured in years. This calculator divides days by 365: for example, 30 days is 30/365 years.
Longer terms often mean more opportunity for price movement and higher option values, but 180-day options are not invariably dearer than 30-day options. Dividends, rates, deep-ITM European puts and different term IVs may change the comparison.
Theta measures price change as calendar time passes, all else equal; here it is per day. ATM decay often accelerates near expiration, but Theta is nonlinear and is not always negative for every long option.
Adapted from the owner's material, with model limitations added.Reference: OIC option pricing factors · Theta learning resources. Fixed model inputs do not mean real market conditions stay fixed.