What we usually call American crude oil futures refers to the WTI crude oil contract listed in the New York Mercantile Exchange, that is, American West Texas light crude oil. Specific delivery date setting (the time mentioned here is based on Beijing time, of course, from conversion of time, USA):
If 25th of the month is a working day, then the last trading day of WTI contract in the first month of the month is the third trading day before 25th; If 25th of the current month is a non-working day, the last trading day of WTI contract in the first month of the current month is the third trading day before 25th. Usually around the 20th of every month.