Exploit differential time decay by selling near-month options and buying far-month options at the same strike.
A Calendar Spread (also called a Time Spread or Horizontal Spread) involves selling a near-term option and buying a longer-term option at the same strike price. The strategy profits from the fact that near-term options decay faster than longer-term options due to the non-linear nature of theta decay.
The key insight is simple: time value erodes faster as expiration approaches. A weekly Nifty option with 3 days to expiry loses time value much faster than a monthly option with 25 days to expiry, even at the same strike. By selling the fast-decaying option and buying the slow-decaying one, you capture this differential decay as profit.
Calendar spreads are ideal for traders who expect the underlying to stay range-bound in the short term but want to maintain a longer-term position. On NSE, the most common calendar spread involves selling the current weekly Nifty expiry and buying the next weekly or monthly expiry at the same strike.
Unlike directional strategies, a calendar spread has its maximum profit when the underlying closes at the strike price on the near-term expiration date. This makes it a neutral strategy that bets on time rather than direction.
Near-Month = Option you sell (current weekly or monthly expiry)
Far-Month = Option you buy (next weekly or monthly expiry)
Max Loss = Net debit paid (occurs if underlying moves far from strike)
Ideal Outcome = Near-month expires worthless while far-month retains significant value
Calendar spread profit forms a bell curve centered at the strike. Maximum profit when underlying stays at the strike; losses if it moves too far in either direction.
Nifty is at 24,500 on Monday. You expect range-bound action this week but want theta exposure.
Sell 1 lot Nifty 24,500 CE (this Thursday expiry) at ₹85
Buy 1 lot Nifty 24,500 CE (monthly expiry, 25 days away) at ₹210
Net Debit: 210 - 85 = ₹125 per unit = ₹125 x 25 = ₹3,125
Scenario 1 (Ideal): Nifty closes at 24,500 on Thursday. Weekly CE expires worthless (you keep ₹85). Monthly CE still worth ~₹185 (lost some theta but still has 21 days). P&L = (85 + 185 - 210) x 25 = ₹1,500 profit
Scenario 2 (Bad): Nifty rallies to 24,800 by Thursday. Weekly CE expires at ₹300 (you lose ₹215). Monthly CE is worth ~₹340. P&L = (-215 + 340 - 210) x 25 = -₹2,125 loss
Scenario 3 (Bad): Nifty drops to 24,100 by Thursday. Both options lose most value. Weekly CE expires worthless (you keep ₹85). Monthly CE worth ~₹55. P&L = (85 + 55 - 210) x 25 = -₹1,750 loss
After the weekly expiry, you still hold the monthly CE. You can sell another weekly against it the following week, creating a repeating calendar strategy.
The near-month option decays at roughly 2-3x the rate of the far-month option. This differential is highest when the underlying is at the strike price, driving maximum profit.
As the near-month expiry approaches, the profit zone narrows. The position becomes more sensitive to price moves. Early in the trade, the zone is wider and more forgiving.
Theta decay accelerates in the final week. A Nifty weekly option loses about 50% of its remaining time value in the last 2 days, making this period the most profitable for calendar spreads.
Enter calendar spreads 5-7 days before the near-month expiry. Too early and you tie up capital with slow decay; too late and the cost of the spread may not justify the limited profit potential.
When Nifty is consolidating in a narrow range (200-300 points) and you expect this to continue through the near-term expiry.
When you want to earn from time decay without the unlimited risk of naked option selling. Calendar spreads have defined maximum loss.
When India VIX is below 13 and you expect it to stay stable or rise slightly. The long Vega position benefits from any IV expansion.
Best when there are no major events before the near-month expiry. Events can cause large moves that push the underlying away from your strike.
A diagonal spread is a calendar spread where the two options have different strike prices in addition to different expiry dates. For example, sell the current weekly 24,500 CE and buy the monthly 24,600 CE. This adds a directional bias (in this case, slightly bullish) to the time spread.
Buy a deep ITM LEAPS call (high Delta, long-dated) and sell weekly OTM calls against it. This mimics a covered call position at a fraction of the capital. On NSE, you can buy a quarterly Nifty 23,500 CE (Delta ~0.85) and sell weekly 24,600 CE (Delta ~0.20) against it repeatedly. The deep ITM long call acts as a stock substitute.
After the near-month (weekly) option expires, you still hold the far-month (monthly) option. You can now sell the next week's option at the same strike to create a fresh calendar spread.
Week 1: Sell Thursday expiry 24,500 CE at ₹85. It expires worthless. Profit: ₹85 x 25 = ₹2,125.
Week 2: Sell next Thursday expiry 24,500 CE at ₹78 (slightly less as monthly CE has also decayed). It expires worthless again. Profit: ₹78 x 25 = ₹1,950.
Week 3: Sell next Thursday expiry 24,500 CE at ₹70.
By rolling weekly, you can potentially collect ₹233 in total premium against the original ₹210 cost of the monthly CE, making the entire position profitable even if the monthly CE expires worthless. This is the power of repeated calendar rolling.
Only when the underlying stays near the strike. If Nifty moves 300+ points from your strike, both options lose time value and the spread collapses. Calendar spreads profit from differential decay, not absolute decay.
The far-month option can lose value due to price moves or IV crush faster than you collect weekly premiums. There is always residual risk. Monitor the far-month option value separately.
While they are designed as neutral strategies, calendar spreads lose money on large directional moves. A 500-point Nifty rally can cause significant losses as the short near-month leg goes deep ITM. Always have a stop-loss plan for directional breakouts.
Calendar spreads are net positive Theta near the strike. The short near-month option decays faster than the long far-month option, generating daily income.
Net long Vega exposure. Rising IV benefits the position because the far-month option has higher Vega than the near-month option. A 1% IV rise can add significant value.
When the underlying is at the strike, Delta is approximately zero. Delta becomes positive if underlying drops below strike (as the spread acts slightly bullish) and vice versa.
Short Gamma near the strike. Large sudden moves hurt the position. Near the short expiry, Gamma risk increases. This is why calendar spreads need range-bound conditions.
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