Calendar Spread

Sell near-dated, buy far-dated; profit from time decay differential. Outlook: neutral. Direction: debit. Risk: defined.

A calendar spread (also called a time spread or horizontal spread) is built by selling a near-dated option and buying a far-dated option at the same strike. You pay a small net debit because the long leg is more expensive, but theta on the near leg decays faster than on the far leg, so the spread widens as the near leg approaches expiration.

Calendars are also a term-structure trade: they profit when the near-dated IV collapses more than the far-dated IV. This is exactly the dynamic around earnings and other known events where the weekly IV spikes on the event expiration and then crashes after.

Worked example: a stock trades at $100 with earnings in 7 days. The weekly $100 call (7 DTE, IV 80%) trades at $3.50; the monthly $100 call (35 DTE, IV 35%) trades at $4.50. Open a calendar by selling the weekly and buying the monthly: net debit $1 per share ($100 per contract). After earnings, weekly IV collapses to 35% (matching the monthly); the weekly call decays to its intrinsic value (zero if pinned at $100), and the monthly call is now valued at the new term structure. If the stock pins at $100 through the weekly expiration, the weekly expires worthless and the monthly retains roughly $2.50 of value (deeply IV-crushed but with 28 DTE remaining), so the spread is worth about $2.50 minus the $1 debit = $150 profit per contract. A directional miss (stock to $90 or $110) damages both legs; the monthly's residual value falls and the position approaches the max loss of $100 debit.

Break-Even

No stable closed-form break-even. The P/L at near-leg expiration depends on the residual value of the far-dated leg, which itself depends on far-leg IV and days remaining. The break-even band is narrowest around the short strike and widens when far-leg IV rises. Use the strategy builder for a live break-even curve on a specific ticker.

Max Profit

Achieved if spot is near the strike at near-leg expiration. The near leg expires worthless; the far leg retains most of its value.

Max Loss

Limited to the net debit paid x 100 x contracts. If both legs move deep ITM/OTM together, the spread collapses toward zero.

Risk Profile

Tent-shaped P/L at near-leg expiration: max profit at the strike, falling off in both directions, capped at -debit far away. The shape becomes asymmetric if the term structure is not flat: backwardation pushes the peak left or right depending on which leg has the bigger IV cushion. Calendar P/L is the most term-structure-sensitive of the standard retail strategies.

Greeks by Leg

Two-leg term-structure structure. Short near-dated option contributes negative-but-modest delta, negative gamma (especially as expiration approaches), positive theta (the income source), negative vega. Long far-dated option contributes positive delta of similar magnitude, positive gamma (smaller per-day acceleration), negative theta (slower decay), positive vega (substantial because of the longer expiry sqrt(T) factor). Net: near-zero delta around the strike, mixed gamma (negative locally, positive in time), positive net theta (near-leg theta dominates initially), positive net vega (far-leg vega dominates).

When to Use

• You expect range-bound price action through the near-leg expiration.
• Term structure is in backwardation (near IV > far IV); sell the expensive near leg, buy the cheap far leg.
• Pre-earnings: sell the event-week option, buy the next-month option. Profit from the event-premium collapse.
• You want defined-risk exposure to term-structure dynamics rather than price direction.

IV-Rank Guidance: When to Enter

Calendar spreads benefit most from term-structure backwardation, which often occurs around earnings or other known events. The near-leg IV is elevated relative to the far-leg IV; selling the rich near IV and buying the cheap far IV captures the spread when term structure normalizes. In normal contango (near IV < far IV), calendars are still viable but rely more on pure theta differential. Best entry zones: when the front-back IV spread is at the high end of its 90-day range.

Common Pitfalls

• Big directional moves in either direction kill the spread; both legs go deep ITM or OTM together.
• The position is net long vega (long the far leg vega); general vol expansion helps, but term-structure steepening can hurt.
• Pin risk at the short strike near the near-leg expiration.
• Rolling the short leg (a rolling calendar) adds complexity and transaction costs.

Adjustments and Roll Logic

• If the underlying drifts toward the strike with time remaining on the near leg, the trade is winning: consider taking partial profits at 25-50% of debit.
• If the underlying makes a directional move away from the strike, both legs lose value together; if conviction in the range-bound thesis is broken, close rather than wait.
• After near-leg expiration, you can roll the short leg to a new near expiration ("diagonalize" or extend the calendar) if the directional view stays intact.
• If the near leg expires worthless and the far leg has appreciated meaningfully (rare but possible on vol spikes), close the long leg to lock in the win rather than leaving it as a residual long-vol bet.

Frequently Asked Questions

Calendar vs vertical spread for a neutral view?

Calendars profit from time decay differential AND term-structure normalization; verticals profit only from time decay and the spot landing in the right zone. Calendars have more complex P/L (sensitive to far-leg IV) but also more attractive risk-reward when term structure is in backwardation. Verticals are simpler and more predictable; calendars require more nuance.

How do I size the strikes?

Standard convention is to sell and buy at the same ATM strike, which captures the most theta differential. Diagonalized variants (different strikes) become "diagonal spreads" rather than pure calendars and have additional directional exposure. For a pure neutral term-structure bet, stay ATM.

Can I do put calendars instead of call calendars?

Yes, identical mechanics. Most calendars are call calendars by convention but put calendars work the same way. The choice between them is mostly cosmetic; use whichever fits the broker's order routing better.

What happens if the short leg gets exercised early?

Rare but possible on deep-ITM short calls before ex-dividend (for the dividend) or deep-ITM short puts (for the cash). Early assignment converts the calendar into a long stock + long far-dated option (for short call assignment) or short stock + long far-dated option (for short put assignment). Manage the residual position based on the new exposure.

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