Calendar Spread
A calendar spread is an options or futures strategy that involves simultaneously entering long and short positions on the same underlying asset and strike price but across two different expiry months, designed to profit from differences in time decay rates or term structure of volatility.
The calendar spread, also referred to as a horizontal spread or time spread in options markets, exploited the fact that near-month options lost time value (theta) faster than far-month options. In its most common options form, a trader would write a near-month at-the-money option and purchase the same strike in a later expiry month, resulting in a net debit. The expectation was that the written near-month option would decay faster than the long far-month option, allowing the position to be closed at a profit.
On NSE, options were available in weekly Nifty expiries (introduced in 2019) as well as monthly expiries for both index and stock options. The availability of weekly contracts dramatically expanded calendar spread opportunities. A trader who was neutral on the near-term direction but expected elevated volatility in the following month could express that view through a calendar spread, paying relatively little net premium while maintaining defined risk equal to the initial net debit.
In the futures segment, calendar spreads took a different form. A trader might simultaneously hold a long position in the current-month futures contract and a short position in the next-month contract (or vice versa). The profit or loss was driven not by the absolute price of the underlying but by the change in the spread between the two contract prices — a function of carrying costs, dividends, and market expectations. This was a popular strategy among institutional arbitrageurs and algorithmic traders who monitored the roll yield between near and far contracts.
The risk profile of a calendar spread was more complex than directional spreads. At expiry of the near-month option, the ideal outcome was for the underlying to be exactly at the strike price, maximising the time value retained in the far-month long option. A large move in either direction at near-month expiry could result in a loss, because the written option's value would increase sharply while the far-month option might not increase proportionally (vega differentials between expiries). This dual sensitivity to direction and volatility made calendar spreads better suited to experienced traders who could monitor both dimensions.
SEBI's introduction of physical settlement for stock derivatives and the phased expansion of weekly options across individual stocks added nuance to calendar spread execution. Traders had to be aware of different settlement obligations across expiries and ensure adequate margin was maintained for each leg independently, even when the net risk of the combined position was limited.