Calendar spread contracts: These spread contracts are defined over the price difference of two futures contracts having the same underlying, but different maturities. To understand this better, let’s consider Bitcoin futures spread contract. This contract is defined as the difference in price of a longer-dated BTC futures (e.g. BTC December futures) and the price of a shorter-dated BTC futures (e.g. BTC September futures). Therefore, a position in the BTC futures spread contract represents a long and short position in the two underlying futures contracts.