Calendar Spread

A calendar spread (also called a time spread or horizontal spread) involves selling a near-term option and buying a longer-term option at the same strike price. The strategy profits from the faster theta decay of the short-term option relative to the long-term option. You're essentially arbitraging the different rates of time decay across expirations.

When to Use a Calendar Spread

Calendar spreads work best when:

• You expect the stock to stay near the strike price (neutral outlook)
• Near-term implied volatility is higher than longer-term IV
• You want to profit from time decay with limited risk
• A catalyst (earnings, etc.) falls between your two expirations

The Setup

• Max Profit: Achieved when stock closes exactly at the strike price at front-month expiration
• Max Loss: Net debit paid (if stock moves far from the strike)
• Breakeven: Depends on remaining IV and time value — not fixed at entry
• Vega profile: Positive vega on the back-month, negative on the front-month; net positive vega exposure

Example

Stock trading at $100. You sell the 30-day $100 call for $3 and buy the 60-day $100 call for $5:

• Net debit: $2 ($200 per contract)
• Max loss: $2 ($200) if stock moves significantly away from $100
• Max profit: Variable, but often 50-100%+ of debit paid if stock pins at strike

At front-month expiration, if the stock is at $100, the short call expires worthless and the long call retains significant value, creating profit.

How Calendar Spreads Profit

The key insight is that options decay faster as expiration approaches. A 30-day option loses time value much faster than a 60-day option. By selling the faster-decaying option and owning the slower-decaying one, you capture this differential.

The ideal scenario: the stock stays near the strike, the short option decays to zero, and you're left with a long option that still has substantial value.

Risks and Greeks

Calendar spreads have unique risk characteristics:

• Vega risk: Rising IV helps (long option gains more than short option loses), but falling IV hurts
• Directional risk: Large moves in either direction hurt the trade
• Gamma risk: Negative gamma near expiration of the short option

Earnings Calendars

A popular variation is placing the short expiration before earnings and the long expiration after. You profit from:

1. Theta decay on the short option
2. IV increase in the long option as earnings approach
3. IV crush hitting the short option harder if it's closer to the event

Common Mistakes

1. Wrong IV structure: If near-term IV is lower than long-term, the spread may not work
2. Stock moves too much: Large moves destroy calendar spread value
3. Ignoring assignment risk: Short options can be assigned, especially around dividends
4. Holding past front expiration: Manage the trade before the short option expires

Calendar spreads are sophisticated strategies that benefit from neutral price action and favorable volatility dynamics. They require more active management than simple directional trades.