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Calendar Spread

OVERVIEW

A calendar spread — also called a time spread or horizontal spread — is an options strategy that simultaneously sells a near-term option and buys a longer-dated option at the same strike price on the same underlying asset. The net position costs a debit (back-month premium minus front-month premium). Profit accumulates when the front-month option decays faster than the back-month, or when implied volatility rises (which inflates the back-month option's value more than the front-month's). The maximum profit occurs when price closes exactly at the strike on front-month expiration day.

Note

Both calls and puts can form calendar spreads. At-the-money strikes produce the most theta-efficient setup.

CONSTRUCTION AND VALUATION

Setup

Leg Action Strike Expiry
Short leg Sell 1 call (or put) K Front month
Long leg Buy 1 call (or put) K Back month

Net debit = Back-month premium − Front-month premium

P&L at front-month expiration

At expiration of the short leg, the position value equals the remaining extrinsic value of the long back-month option minus any intrinsic loss on the short leg. Peak value occurs at K; losses mount as price moves away in either direction.

Greeks

Greek Direction Explanation
Theta Positive Short front-month decays faster in dollar terms than the long back-month
Vega Positive Longer-dated options are more sensitive to volatility changes; a 1-point IV rise adds more value to the back-month than to the front-month
Delta Near zero (ATM) Becomes directional as price moves away from the strike
Gamma Negative Short front-month carries higher gamma than the long back-month near expiration

WORKED EXAMPLE

Underlying: AMZN at $128 (September 2023), low realized volatility between earnings periods.

Action Strike Expiry Premium
Sell 1 call $128 October (15 DTE) $2.40 credit
Buy 1 call $128 November (45 DTE) $4.80 debit
Net debit $2.40 ($240/contract)

Outcome at October expiration — AMZN closed at $129

Component Value
Short $128 call (expired) $1.00 intrinsic
November $128 call (30 DTE remaining) $4.20 time value
Net position value $3.20
Profit $0.80 ($80/contract, ~33% return on capital)

Tip

If AMZN had moved to $140 or $116, both legs would have converged toward intrinsic value, eliminating the time-value differential and generating a loss.

USE CASES

Range-bound expectations When a stock is expected to stay near a specific level, the calendar extracts theta without requiring a directional call.

Pre-earnings volatility structure trades If near-term IV surrounding an earnings date is elevated relative to back-month IV, selling the front-month captures the vol premium while the back-month provides lower-cost long exposure to any post-earnings move.

Low-cost long-volatility exposure Buying a calendar costs less than buying a naked option with the same vega, serving as a capital-efficient way to be long implied volatility.

Strike selection for thesis-driven setups Traders who expect a stock to gravitate toward a technical level — support, VWAP, previous close — can center the calendar at that level.

LIMITATIONS

A large move in either direction before front-month expiration turns the calendar into a loser — the setup has negative gamma and suffers on gap moves. Early assignment risk on the short leg is real when it goes deep in the money, particularly for calls ahead of ex-dividend dates. A volatility collapse in back-month options can erode the position even if price stays at the strike, because the vega loss on the long leg outweighs theta gains. Liquidity in back-month strikes is lower than in front-month options, widening bid-ask spreads and making mid-position adjustments expensive.

Note

"Calendar spreads always profit from time decay" is incomplete. The spread profits from the differential decay rate, and that differential collapses when the stock moves away from the strike.