Expiration refers to the maturity date of forward contracts (futures and options) and discharge of obligations thereunder.
Expiration for options means the last date on which the option holder can demand the exercise of this option in accordance with the terms of the contract.
Exchange-traded derivatives usually have their expiration calendar. Calendars are determined in advance as a matter of convenience for traders.
Before the expiration of derivative contracts, strong price movements may occur. This is due to both speculative trading and the transfer of funds of market participants to the derivative contract with the next expiration date. Consequently, volatility may increase significantly. At the same time, as the expiration date approaches, the difference between the price of the derivative contract and the price of the underlying asset decreases, and the spread tends to zero.