A double calendar spread combines two calendar spreads—one on the call side and one on the put side—at different strikes above and below the current stock price. By placing one calendar at a call strike above the market and another at a put strike below, you create a position with two time-spread profit zones that benefit from the underlying staying range-bound while front-month options decay faster than back-month options.
Each component calendar spread benefits when the underlying stays near its respective strike. The double calendar thus creates a wider combined profit zone than a single calendar, with maximum profit at either the call strike or the put strike (wherever the stock ends up). The position profits most if the stock drifts from one strike toward the other during the front-month period, allowing one calendar to approach full profit while the other retains value.
Double calendars are particularly effective in low-IV environments where you expect the underlying to remain range-bound. The strategy benefits from IV expansion (both back-month options gain value) and from time decay differential. In contrast to iron condors (which benefit from IV contraction), double calendars welcome a moderate increase in volatility because the long back-month options have positive vega.
The strikes for a double calendar are typically placed at one standard deviation above and below the current price, or at the expected one-week or two-week move boundaries. This places the short options in a zone where time decay is most efficient while giving the structure enough room to accommodate modest price movement.
Management of double calendars involves closing when sufficient time decay profit has been captured from the front month (often 7-14 days before front-month expiration to avoid gamma risk), then either exiting the back-month options or rolling to create new calendars with the next front-month expiration.