A calendar spread profile in an options calculator is not a P&L forecast

Most options calculators model a calendar spread profile at the expiration date of the front leg. And there is an important nuance here. If an options structure is built within the same expiration cycle, the payoff profile we see at entry generally corresponds to what we will get at expiration. With calendars, the situation is different. The profile we see at entry and the profile we actually get by the expiration of the short legs can be quite different. The reason is simple: a calendar is not only a bet on the underlying price movement, but also a bet on volatility. While the position is alive, IV changes, the value of the long and short options changes, and the entire shape of the position changes along with it. The video shows exactly this kind of example. The green dashed line is the modeled profile of a double calendar at the expiration date of the short legs, calculated at the moment the position was opened. Then the video shows how the position actually evolved using historical option prices. It also clearly shows how changes in IV affect the value of calendar spreads. As the market dropped, IV increased, and the profile improved noticeably. A small reminder for newer traders: when trading calendar spreads, you should not treat the expiration profile as a ready-made picture of the future. What you see at entry is not a forecast of your future P&L. It is only a calculated snapshot based on the current market parameters.