For most of the last decade, trading index options in India meant building the week around Thursday. Nifty, Bank Nifty, and Sensex weekly contracts largely expired on the same day, and market activity concentrated around that single session. That structure has been rewritten in two phases since late 2024, and by September 2025 the weekly calendar looked materially different.
What changed
Phase one, October 2024. SEBI issued a circular, effective 20 November 2024, restricting each exchange to offering weekly expiry contracts on only one benchmark index rather than several. The regulator's stated concern was that concentrating short tenor options activity across multiple indices on the same day was amplifying speculative churn and producing sharp price swings, particularly for retail participants. Following the circular, NSE retained weekly expiry only on Nifty 50, with Bank Nifty, FinNifty, and Nifty Midcap Select moving to monthly expiry only. BSE retained weekly expiry only on Sensex, with Bankex and Sensex 50 shifting to monthly.
Phase two, September 2025. Having narrowed each exchange to a single weekly index, SEBI then directed the exchanges to spread that expiry across different days of the week instead of clustering on Thursday. Effective 1 September 2025, NSE moved Nifty 50's weekly expiry from Thursday to Tuesday. Effective 4 September 2025, BSE moved Sensex's weekly expiry from Tuesday to Thursday. Monthly expiries for both indices follow the same logic: Nifty on the last Tuesday of the month, Sensex on the last Thursday, with expiry shifting to the previous trading day whenever the scheduled date falls on a market holiday.
The net effect is that instead of one concentrated Thursday, the trading week now has two separate expiry pressure points: Nifty on Tuesday and Sensex on Thursday, each with its own liquidity profile and participant base.
Why the change matters beyond the calendar
Expiry day is typically where options time value decays fastest, open interest unwinds most sharply, and intraday price action tends to be most pronounced. Moving that day changes which sessions in the week carry that behaviour, and several downstream effects have followed.
The pre expiry session has shifted. With Nifty expiry now on Tuesday, Monday has become the effective run-up session, the day when positioning ahead of expiry typically builds. That also means weekend global news and Monday gap risk now feed more directly into Tuesday's expiry dynamics than they did when Thursday was the sole focal point.
Turnover has redistributed between exchanges. Analysts had projected the schedule change would narrow BSE's share of index options turnover from roughly 24 percent to around 21 percent, with NSE absorbing the difference, though BSE's Thursday slot has also drawn increased attention in part because Thursday coincides more often with mid week events such as RBI policy announcements.
Liquidity and spreads differ across the two expiry days. Because Sensex options carry comparatively lower liquidity than Nifty options, bid-ask spreads on BSE's Thursday expiry, particularly for strikes further from the money, tend to run wider than on NSE's Tuesday session, a factor that affects position sizing and execution cost on that leg of the week.
Decay and gamma exposure now cluster on two separate days rather than one. For traders running weekly strategies across both indices, this means two distinct risk windows to plan around each week instead of a single one, each with its own liquidity and spread characteristics. Reading open interest changes and the put-call ratio ahead of each expiry, a practice sometimes referred to as derivatives analytics, is one way traders track how positioning is building into each of these two sessions separately rather than treating the week as a single event.
How traders have adjusted
The practical shifts under discussion among market participants center on a few themes.
Entry timing for premium selling strategies has moved. Traders who previously timed entries around a Thursday expiry are adjusting those windows to fit a Tuesday cycle, while weighing the added weekend gap risk that now sits between a Friday entry and a Tuesday expiry.
Tuesday and Thursday are increasingly treated as two separate planning cycles rather than one weekly routine, with traders building separate pre-expiry checklists, covering open interest changes, implied volatility shifts, and liquidity by strike, for each index independently given how differently the two sessions behave.
Holiday shift rules have become part of routine planning. Since expiry moves to the previous trading day whenever the scheduled Tuesday or Thursday falls on a holiday, traders are building exchange holiday calendars directly into expiry planning rather than assuming a fixed weekday every time.
The broader context
This reform sits within a wider set of SEBI changes to India's derivatives market since 2023, including larger contract sizes and additional margin requirements around expiry, against a backdrop of continued scrutiny of retail losses in short dated options. SEBI's own FY26 data put aggregate net losses for individual derivatives traders at roughly Rs 91,685 crore, with the bulk concentrated in options expiring the same week they were entered. The number of active individual derivatives traders itself fell about 18 percent to roughly 87.5 lakh over the same period, even as the aggregate loss figure remained elevated, a combination that regulators have pointed to as evidence that the earlier concentration of activity around single expiry sessions was disproportionately affecting less experienced participants. Reports have also floated a further proposal to reduce or remove weekly expiries altogether, though SEBI had not confirmed any such move as of the time of writing.
The pattern behind these changes has been consistent: regulatory intent to de-concentrate risk that had built up around a single high-volume session, met by a market structure that continues to adjust in response. For anyone actively trading index options, understanding why the calendar changed, not only which day is which now, is generally what helps in adapting a strategy rather than simply memorizing a new weekday. Building that kind of process, one that holds up across changing market structure rather than being tied to a single day of the week, is typically the outcome of structured, mentor-led practice such as a multi-asset trading mentorship program, rather than something picked up from a single rule change alone.
This article is for informational and educational purposes only and does not constitute trading or investment advice. F&O trading involves substantial risk of loss and is not suitable for all investors.
