Calendar Spread

Q: What is a calendar spread?

A calendar spread, also called a time or horizontal spread, sells an option on a near expiry and buys an option of the same type and strike on a later expiry. It is entered for a net debit, because the longer-dated option costs more. The position earns money if the near option loses its time value faster than the far option, which happens when the underlying stays close to the strike.

Q: When does a calendar spread make the most money?

At the near expiry, with the underlying at the strike. The short near option then expires worthless and the long far option retains the most time value it can have, since at-the-money options carry the most. The further the underlying moves from the strike in either direction, the less the position is worth.

Q: Is a calendar spread long or short volatility?

Net long. The far option has more vega than the near one, so a rise in implied volatility helps the position and a fall hurts it. It is also exposed to the term structure: the spread gains if far-expiry IV rises relative to near-expiry IV, and loses if the near expiry's IV spikes while the far stays put, as can happen ahead of an event inside the near week.

Q: What is the maximum loss on a calendar spread?

The net debit paid, provided both legs are held to the near expiry and the far leg is then closed or kept. If the underlying moves far from the strike, both options lose most of their value and the spread approaches its maximum loss. The loss cannot exceed the debit because the long far option always covers the short near option at the same strike.

Q: How does margin work on a calendar spread in India?

The short near option would normally attract full SPAN and exposure margin, but because it is hedged by a long option on the same underlying and strike, NSE's SPAN gives a calendar-spread margin benefit, so the blocked amount is well below a naked short. The benefit disappears once the near leg expires or is closed, leaving a plain long option.

Two expiries, one strike. The spread sells the clock on the near contract and buys it on the far, and wins when the market goes nowhere in particular for a week.

In short: a calendar spread sells an option on the near expiry and buys the same strike and type on a later expiry, for a net debit. It profits from the near option's faster time decay and from a rise in implied volatility, and does best when the underlying sits at the strike on the near expiry. Maximum loss is the debit. On NIFTY the natural version is short the Tuesday weekly against long the monthly at the same strike.

The intuition

Time decay is not linear. An option with six days left loses value far faster per day than the same strike with thirty-four days left, because the near contract's remaining time is a larger share of what it has. A calendar spread exploits that difference: it is short the fast-decaying contract and long the slow one. If the underlying stays near the strike, the near option goes to zero while the far option keeps most of its value, and the spread widens.

The position is also net long vega, because a longer-dated option responds more to a change in implied volatility. A calendar is therefore a bet on two things together: the index staying put for the near expiry, and implied volatility holding or rising. A sharp move in either direction, or a collapse in IV, works against it.

Worked example (illustrative numbers)

Suppose NIFTY is at 24,000 on a Wednesday, with the weekly expiring next Tuesday (6 days) and the monthly 34 days out, both at 14% implied volatility:

Sell 24,000 call, 6 days	receive ₹185
Buy 24,000 call, 34 days	pay ₹484
Net debit	₹299 per unit, ₹19,435 per lot (65)
Maximum loss	₹19,435 (the debit)

At the weekly expiry the short call settles at its intrinsic value and the long call has 28 days left. Its value depends on where NIFTY is and on IV; holding IV at 14%:

NIFTY at weekly expiry	Short weekly settles at	Long monthly worth	Spread value	P&L per lot
23,400	0	₹175	₹175	−₹8,060
23,700	0	₹285	₹285	−₹910
24,000	0	₹433	₹433	+₹8,710
24,300	₹300	₹619	₹319	+₹1,300
24,600	₹600	₹839	₹239	−₹3,900

The peak is at the strike. The spread's profitable range runs roughly from 23,700 to 24,400, about 1.5% either side, and outside it the position loses. If implied volatility on the monthly rose from 14% to 17% over the week with NIFTY unchanged, the long call would be worth about ₹512 instead of ₹433, adding ₹5,135 per lot; the reverse move would cost the same. The tent-shaped payoff and the volatility sensitivity are the two things to hold in mind.

The calendar's tent at the near expiry. The dashed curve shows the same spread if the monthly's implied volatility is higher when the weekly expires.

Why it matters to an options trader

It is a way to be short the weekly without naked risk. The long monthly caps the loss; a plain short weekly does not.
It trades the term structure directly. When near-expiry IV is high relative to far-expiry IV, the spread is cheap to enter and has the structure working for it as the near IV decays.
It converts a range view into a position. A trader who expects a quiet week but a volatile month has exactly this shape of exposure.
It is the building block of diagonal and double-calendar structures. Shifting the far strike gives a directional tilt; adding a put calendar gives a wider tent.

Common mistakes

Treating it as a pure theta trade. The vega exposure is as large as the theta exposure; a quiet week with falling IV can still lose money.
Entering before an event inside the near week. Near-expiry IV spikes relative to the far, which is the wrong way round for this spread; enter after the event or choose expiries that straddle it deliberately.
Leaving the long leg unmanaged after the near expiry. Once the weekly is gone the position is a plain long monthly with a different risk; decide in advance whether to close it or roll the short leg.
Ignoring early assignment on stock options. NSE stock options are European, so this does not apply in India, but the short leg of a stock calendar held into expiry faces physical settlement.
Using illiquid far strikes. The monthly's bid-ask at an off-centre strike can eat the expected edge; stay near the money where both expiries trade.

Indian-market specifics

On NIFTY the natural calendar is the current Tuesday weekly against the monthly (last Tuesday), or one weekly against the next. Bank Nifty, FinNifty and Midcap Select have monthly expiries only since November 2024, so their calendars span months, not weeks.
Sensex offers the same structure on BSE with Thursday weeklies and a last-Thursday monthly.
NSE's SPAN margin recognises the calendar hedge and charges far less than a naked short; the benefit lapses when the near leg expires at 15:40 on expiry day, so the margin on the remaining long leg is just its premium.
Both legs are cash-settled on index options. STT on the sale of the near leg's premium is 0.15% from 1 April 2026; if the near leg finishes in the money its exercise is also taxed on the intrinsic value.

FAQ

What is a calendar spread?

Short a near-expiry option, long the same strike on a later expiry, for a net debit.

When does a calendar spread make the most money?

At the near expiry with the underlying at the strike.

Is a calendar spread long or short volatility?

Net long, and exposed to the gap between near and far implied volatility.

What is the maximum loss on a calendar spread?

The net debit paid.

How does margin work on a calendar spread in India?

SPAN gives a calendar hedge benefit on the short leg, which lapses when the near expiry settles.

Both expiries, side by side

The NIFTY option-chain page shows the weekly and monthly chains with implied volatility at every strike, so the two legs of a calendar can be priced together. In the app, the option chain can be switched between expiries, so the near and far legs can be priced at the same strike.

NIFTY option chain Calendar spreads guide

Related terms

Term Structure, the IV gap the spread trades
Theta Decay, why the near leg loses faster
Weekly Expiry, the near leg on NIFTY
Vega, the spread's second exposure