Order Duration
Also called: good til canceled, GTC, day order, fill or kill
Order duration sets how long an unfilled order stays live: a day order expires at the close, good-til-canceled persists for weeks, immediate-or-cancel takes what it can and drops the rest. The detail that catches people is that GTC orders sit forgotten and then fill during a crash or a spike months later, at a price that made sense under conditions that no longer exist.