Contract roll is the process of closing or offsetting a futures position in one contract month and establishing a replacement position in a later contract month to maintain substantially similar market exposure. The expiring contract is not extended: one maturity is exited and another is entered, usually before expiry, settlement or—where relevant—notice and delivery procedures become operationally important.
Changing maturity without leaving the market
A trader who is long the expiring contract typically sells it and buys a deferred contract; a short trader buys back the expiring contract and sells the deferred contract. The legs can be executed separately, but exchange-listed calendar spreads often allow the closing and opening legs to be traded together. That reduces the time gap between them and therefore the risk of slippage from an intervening market move. A calendar spread is not automatically a contract roll, however: the same structure can also be held as a relative-value position between maturities.
The replacement contract normally trades at a different price because it sits at a different point on the futures term structure. That price difference is part of the roll transaction, but contract roll should not be treated as a synonym for roll yield. Contract roll describes the transfer of exposure from one maturity to another; roll yield is a return concept associated with maintaining futures exposure through successive contracts and with how those contracts behave as time passes.
Roll date is not the same as deadline
There is no universal roll date. Timing depends on contract rules, liquidity, delivery or settlement mechanics and the trader's objective. Liquidity can migrate to the next contract before the nearby contract stops trading. CME Group's equity-index documentation, for example, publishes customary roll dates while stating that participants may roll from one quarterly month to the next at any time they choose. The practical lesson is that a quoted “roll date” may describe a liquidity convention rather than a mandatory exit date.
Rolling the same number of contracts also does not always preserve the same risk exposure. CME Group's Treasury-futures documentation notes that nearby and deferred contracts can have different DV01, so a fixed 1:1 roll can change portfolio duration even though the contract count is unchanged. The same implementation issue appears in research: a continuous futures series must define when it switches contracts and which contract replaces the old one. Fixed-date, days-to-expiry and liquidity-based roll rules can therefore produce different historical series, affecting charts, indicators and backtests.