Each futures product lists several expiries. Index futures use quarterly months: March (H), June (M), September (U), December (Z). Energy and metals list monthly. The ticker combines root, month code, and year: ESZ5 is the December 2025 S&P contract.
Traders mostly use the front-month and roll to the next one before expiry. Holding a physically settled contract past first-notice-day can create delivery obligations.
Example: in early September, ESU (September) is the front month. Around the second Thursday of September volume shifts to ESZ (December).
Related: front-month, roll, first-notice-day, settlement