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Calendar spreads, or time spreads, describe the price differential – or spread – that may arise between differently dated futures contracts. For example, the price difference between contracts for first- and second-month light, sweet crude offered on Nymex. Time spreads can be mitigated by purchasing options on the difference between average annual prices. In effect, such options provide protection against a reshaping of the forward price curve.
The term is also used for trading in which the parties buy a certain number of futures contracts for a specific month and simultaneously sell the same number of futures contracts for a different month.