An options strategy involving the simultaneous purchase and sale of two options of the same type and strike price but with different expiration dates. Also known as a calendar spread or time spread, it profits from the difference in time decay between the two options.
Example
“A trader set up a horizontal spread on AAPL by selling a near-term $180 call expiring in two weeks and buying a $180 call expiring in six weeks, profiting as the short option decayed faster.”