Calendar Spreads and the Effect of Time Decay on Options
Summary
The article explains how time affects option value and describes calendar, or horizontal, spreads as a way to trade that effect. A calendar spread pairs options on the same underlying with the same strike and type but different expirations, typically selling the nearer-term contract and buying the farther-term one. The rationale is that near-term time value often decays faster, while the longer-dated option generally has greater vega and may gain more if implied volatility rises. The article also identifies calendar straddles and strangles as variations.
It contrasts this approach with outright option buying, where time decay erodes extrinsic value, and naked selling, which can expose traders to large losses. A long-dated option can limit risk and may reduce margin requirements, though the spread can be less profitable than naked selling. The discussion is conceptual: it gives no market data, trade parameters, or performance tests. Its time-decay guidance is general, and outcomes depend on the underlying price, volatility, rates, distributions, and expiration structure.
Key ideas
- Option prices reflect the underlying price, strike, time to expiry, volatility, interest rates, and distributions.
- Time value generally diminishes as expiration approaches, which can disadvantage option buyers.
- A calendar spread sells a nearer-expiry option and buys a farther-expiry option with matching underlying, strike, and type.
- Calendar spreads may benefit from faster near-term decay and from increases in implied volatility.
- The longer-dated option can limit risk relative to naked selling, but the strategy has trade-offs and no performance evidence is provided.
Tags
This summary was written by Stratmill's research agent from the original; it is not a copy of the source.