You have a first options strategy working on daily signals. It buys a call when your underlying closes above its 50-day average, then exits after five sessions. Your backtest has plausible prices, fees, and position sizing. The trouble is that it treats “five sessions” as if every option contract were still the same instrument for those five days.
Before you tune the signal, give each contract a calendar. An option’s expiration date, last trading time, settlement method, and exercise rules determine when its price can be observed and when the position can still be changed. Those details can turn an ordinary holding period into a different trade.
Which clock does your option follow?
Your underlying may trade while the option market is closed, and the option may stop trading before the date printed as expiration. For a US equity option, the regular session generally ends at 4:00 p.m. Eastern, while some products have different closing times. A weekly option expiring Friday also does not mean you can submit an order after the market closes Friday and receive a Friday fill.
Write down the relevant times for the specific product and venue you model. Keep the session calendar, time zone, early closes, and final trading cutoff with the contract data. A generic weekday calendar will miss holidays and shortened sessions. If your data labels a contract with a date but gives no last-trade timestamp, you have not yet established when the backtest can exit.
| Contract detail | What your backtest needs | What can go wrong |
|---|---|---|
| Expiration | The product’s actual expiration convention | Holding a contract past its last trade |
| Settlement | Physical delivery or cash settlement | Inventing shares or cash flows at expiry |
| Exercise style | When exercise may occur | Ignoring early assignment on short options |
| Trading session | Last eligible order time and calendar | Filling during a closed or shortened session |
Why does settlement change your position?
Suppose your call is in the money at expiration. With physical settlement, exercise can create a stock position: one standard US equity call typically represents 100 shares, subject to contract adjustments. A backtest that simply deletes the option at expiration has skipped the resulting stock exposure and cash movement. If you intended to close before expiration, your simulated order needs to happen before the contract’s last trading time.
Cash-settled index options have a different problem. Their final settlement value may be calculated from a special opening or closing process, rather than the ordinary quote you see in your options history. If your strategy holds through that calculation, using the underlying’s nearest bar close as the settlement price can create a result that no account received.
And if you are short an American-style option, early assignment can leave you holding stock before expiration. You may not be able to infer assignment perfectly from a daily options bar. State your assumption, and keep it consistent between the backtest and paper strategy. A model that assumes no early assignment is not a neutral default; it is a specific simplification.
How should your five-session exit work?
Count sessions in the option’s trading calendar, not generic dates. At each decision point, identify the exact contract you hold, check whether it remains eligible to trade, and define what happens if your planned exit falls after its last trading time. You might roll on the preceding session, close at the last available quote, or allow settlement and model the resulting asset. Each choice describes a different strategy.
For example, a five-session holding period entered Monday can span a Friday expiration. If the position is a same-week option, your fifth-session exit may be impossible as written. Moving the exit to Thursday changes the holding period. Rolling into the next expiry changes the contract and adds spread, fees, and a new volatility exposure. Record that choice in the strategy logic instead of letting the data loader quietly pick the next listed symbol.
Keep a contract ledger with, at minimum, the underlying, expiration, strike, right, multiplier, settlement type, exercise style, session calendar, and final trading timestamp. Store contract adjustments too; a corporate action can change deliverables while leaving a familiar ticker behind.
What should you check before trusting the result?
Take one position that reaches expiration and trace it from entry to final disposition. Confirm that every quote belongs to that contract, that your exit occurs while trading is allowed, and that the final cash or underlying position matches the product’s settlement rules. Then inspect a holiday week and an early close. Those are where a calendar assumption tends to reveal itself.
Your signal may still be good research after this work. But the result will now describe a trade your system could actually hold, close, or settle. That is the standard you need before comparing option expirations or sending the strategy to paper trading.
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