Calendar Spread: Selling Near Expiry, Buying Further Out

A calendar spread sells an option in a near expiry and buys the same strike in a later expiry. It profits because the near option decays faster than the far one, and it is the only common structure whose edge comes from time rather than from price or structure.

The structure

Leg	Action	Strike	Expiry
1	Sell 1 option	Chosen strike	Near — current weekly
2	Buy 1 option	Same strike	Later — next weekly or monthly

Both legs are the same type — either both calls or both puts — and the same strike. Only the expiry differs, which is why it is sometimes called a horizontal or time spread.

The later option costs more than the nearer one, so the position opens at a net debit. That debit is roughly your maximum risk, though with an important caveat below.

Why it works

Theta accelerates as expiry approaches. An option with three days left loses value far faster than the same strike with ten days left.

A calendar spread harvests that difference. You are short the fast-decaying option and long the slow-decaying one, so each day that passes helps you — provided the index stays near the strike.

The condition it depends on

That proviso is the entire difficulty. The decay advantage is largest at the money, which is also where the position is most sensitive to the index moving away.

The payoff shape

Unlike a vertical spread, a calendar's payoff cannot be written as a simple formula, because the far leg still has time value when the near leg expires.

What is knowable

What you can say precisely:

Maximum profit occurs at the strike, when the near option expires worthless and the far one retains its remaining time value.
Profit falls away in both directions as the index moves from the strike.
Maximum loss is approximately the debit paid, reached when the index moves far enough that both legs behave similarly.
The exact outcome depends on implied volatility at the moment the near leg expires, which is not knowable in advance.

Vega, which cuts the other way

On most selling structures, rising volatility hurts. On a calendar it usually helps, and this surprises people.

You are long the far-dated option and short the near-dated one. The far option has more time remaining, so it is more sensitive to volatility. Net, the position is long vega.

What that means practically

A rise in implied volatility therefore tends to help a calendar spread, and a fall tends to hurt it — the opposite of a short straddle's behaviour.

This has a practical consequence around events. A calendar held through an event can lose from the IV crush afterwards even if the index behaved. That is the reverse of the usual seller's experience and is worth anticipating.

Choosing the strike

At the money maximises the decay advantage and the sensitivity to movement together. Those are the same decision, so there is no setting that gives you one without the other.

Placing the strike slightly out of the money, in the direction you mildly expect, turns the position into a soft directional bet. That is a legitimate variation, provided it is deliberate rather than accidental.

How a calendar behaves as the near expiry approaches

Unlike a vertical spread, a calendar's value changes shape over its life, and the shape is worth anticipating.

Stage	What is happening	Position behaviour
Early	Both legs decaying slowly	Little movement either way
Middle	Near leg decay accelerating	Profit builds if the index stays near the strike
Near expiry	Near leg decay fastest, gamma highest	Most sensitive — profit peaks and can reverse quickly
At near expiry	Near leg settles, far leg retains time value	Outcome determined

The third row is where calendars are won and lost. The decay advantage is largest precisely when the position is most sensitive to the index moving away from the strike.

The tension arrives late

That is the same tension every option-selling structure carries, and it arrives late in a calendar rather than throughout. A position that behaved calmly for days can move sharply in the final session.

What makes calendars difficult

Worth being honest, because they are frequently presented as a low-risk income structure and they are not quite that.

The payoff is not arithmetic. You cannot compute the result in advance the way you can for a vertical spread.
The near leg can be assigned or expire against you. Index options settle in cash, which simplifies this considerably in India, but the near leg finishing in the money still produces a settlement you need to account for.
Liquidity differs between expiries. The far leg often trades thinner, and you pay that spread on entry and exit.
Backtesting is harder. A structure spanning two expiries is more sensitive to how the test handles the roll than a single-expiry structure is.

Automating it

Create two legs, same type and strike

Both calls or both puts, with the same strike rule applied to each.

Set different expiries

The builder lets you choose the expiry per leg — current weekly for the sold leg, next weekly or monthly for the bought one.

Use an at-the-money strike rule

So the strike follows the index rather than being fixed at a level that will be wrong tomorrow.

Set a target and an exit time

A calendar's profit peaks near the near-leg expiry and does not improve indefinitely.

Set the square-off-all-legs rule

A calendar missing its bought leg is a naked short in the near expiry.

Testing it

Does the backtest handle the two expiries correctly, or does it approximate?
What happened in periods when implied volatility fell?
How often did the index stay close enough to the strike to work?
What did liquidity look like at the far expiry in the test period?
After costs across two expiries, is expectancy still positive?

The first question matters more here than for any other structure. A backtest that simplifies the far leg is measuring something different from what you would trade.

The short version

Sell a near-dated option, buy the same strike further out
The edge is the difference in decay rates, not direction
Maximum profit is at the strike, when the near leg expires worthless
Unusually, the position is long vega — rising volatility tends to help
The payoff is not arithmetic; it depends on volatility at the near expiry
Liquidity in the far expiry is the practical constraint

Frequently asked questions

In the final stretch before the near leg expires, when its decay is fastest. That is also when the position is most sensitive to the index moving away from the strike.

Many traders do, because the last portion of the gain carries the most sensitivity. Whether it suits you is a question to settle in backtesting rather than in the moment.

It is harder than a vertical spread, because the payoff depends on volatility as well as price and cannot be computed in advance. A vertical is a better structure to learn on.

Both legs lose most of their value and behave similarly, so the position approaches its maximum loss — roughly the debit paid.

Selling an option in a near expiry and buying the same strike in a later expiry. The edge comes from the near option decaying faster than the far one.

Not inherently. Maximum profit is at the strike, so it is a bet that the index stays close to that level. Placing the strike away from the money turns it into a soft directional view.

You are long the far-dated option, which has more time remaining and is therefore more sensitive to volatility. Net, the position is long vega — the opposite of a short straddle.

Approximately the net debit paid, though unlike a vertical spread it is not exact, because the far leg's value at the near expiry depends on volatility at that moment.

Yes. The builder lets you choose the expiry per leg, so one leg can use the current weekly and the other the next weekly or monthly.

Index options settle in cash, so an in-the-money near leg is settled against the exchange's settlement value. You are left holding the far leg, which still has time value.

They are defined-cost rather than low-risk. The payoff depends on volatility as well as price, which makes the outcome less predictable than a vertical spread of similar cost.

You trade two expiries with different depth, and the far one is usually thinner. That is four spreads crossed in total, which can consume the decay advantage the structure exists to capture.

Start with a free 3-day trial

Build a strategy, backtest it and run it on paper — no broker, no IP and no money needed to try it.

Create a free account

All articles More in Option Strategies