Does the Time Value of an ATM Option Decrease Linearly or Non-Linearly over Time?

The time value of an ATM option decreases non-linearly over time. The decay is slow initially for long-term options but accelerates dramatically in the final months and weeks before expiration.

This non-linear, accelerating decay is characteristic of Theta, and it is most pronounced for ATM options due to their high time value component.

Why Do Options with Longer Time to Expiration Have Lower Daily Theta?
What Is the Practical Implication of Accelerated Theta Decay for an Option Seller?
Why Is Theta Decay Non-Linear, Especially near Expiration?
Why Does Time Decay Accelerate in the Final Month before Expiration?
What Is the Impact of Time Decay on Long-Term Options (LEAPS)?
How Does Theta Decay Accelerate as an Option Approaches Expiration?
Why Is High Gamma Considered a Double-Edged Sword for an Option Trader?
Does Time Decay (Theta) Accelerate or Slow down the Delta’s Movement toward 1.0 as an Option Moves ITM?

Glossar