What it means
Two options can share a strike but expire on different dates, and a reverse calendar seeks to benefit from changes in the gap between those values. Calls pair with calls and puts pair with puts, because using different strikes creates a diagonal rather than the same-strike structure described here.
Unequal contract quantities also change the exposure and should not be silently treated as the standard paired spread. The Options Industry Council describes short call and short put calendars as buying the near option and selling the far option, and its discussion looks for a sharp underlying-price move during the near option's life or a decline in implied volatility.
The position can lose if the underlying stays near the strike as the near option expires. The purchased option may become worthless while the sold option retains time value, and buying back that remaining obligation can cost more than the original credit.
Time decay is therefore not automatically helpful to a premium seller, because the near option is the purchased leg and can lose value quickly. The later option can be more sensitive to increased volatility, which makes the short leg more expensive to close.
Near and far implied volatilities can also move differently around an event. The most important transition is the first expiry.
If the purchased call disappears and the sold call remains, the position can become an uncovered short call with unlimited potential loss, and a remaining short put can create substantial loss if the underlying falls. A risk review must specify what happens before the near option expires, since closing, exercising or allowing settlement can produce different cash flows and positions.
Assignment can create an underlying-asset obligation or position before the trader planned to act, so contract exercise style, settlement and any financing requirements need separate review. Opening premium alone cannot identify breakeven at the first expiry, because the later option still has a market value that depends on price, time and volatility.
Use combined valuation scenarios rather than a single static payoff diagram. For a non-finance manager, ask for the contracts, opening credit, margin requirements and first-expiry plan.
Together these show the size of the position, the cash taken in, the collateral demanded and the planned response when the near option ends.
In practice
Real-world examples.
Example
A fictional trader buys a one-month call for 2 and sells a three-month call at the same strike for 4. The opening credit is 2 per unit. It records cash received, not a guaranteed profit or loss ceiling.
Example
At the first expiry the stock is near the strike and the purchased call expires worthless. The later call is still worth 3. Buying it back creates a 1-per-unit loss against the original 2 credit.
Example
A desk lets its purchased call expire but leaves the sold call open. A later price surge now affects an uncovered short call.
Formula
Calculation
Opening credit per unit = later-option premium received - near-option premium paid. Multiply by the applicable contract size and number of matched contracts.
For a fictional 100-unit contract, premiums of 4 and 2 create a 200 credit before fees. If both legs are later closed, add the amount received for selling the purchased option and subtract the cost of buying back the sold option.
If the near option expires worthless and closing the far option costs 3 per unit, the result is 200 -300 =-100 before fees. If the later obligation is left open, this calculation is not the final outcome.
No fixed breakeven follows from the opening credit alone while the expirations differ.Case study
Seen in the real world.
Fictional case study: Willow Options opens reverse calendars before a company announcement. The event passes without a large price move, and the short-dated calls approach expiry near their strikes. A junior analyst celebrates the opening credit.
The risk manager instead values the remaining later calls and finds that closing them would cost more than that credit. The desk closes the paired positions and records a loss rather than leaving uncovered obligations. Its revised report shows combined values and the first-expiry decision, separating received premium from realised performance.
Watch out
Common mistakes.
- Calling the opening credit the maximum loss. Remaining short options and volatility changes can create much larger losses.
- Letting the near option expire without reviewing the later short leg. The remaining position can have different and severe risk.
- Assuming a call version is always bearish or a put version always bullish. Evaluate the actual price, volatility and timing exposures.
Questions
People also ask.
How is this different from a long calendar?
The near and far long-short positions are reversed, changing time decay and the position left after the first expiry.
Can it use puts?
Yes. Both legs should be puts of the stated matching structure. The remaining short put can still carry substantial downside risk.
Does it always profit from a large move?
No. The combined values, timing, implied volatilities and execution costs determine the result. A market move alone is not proof of profit.
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