If something is mistimed, it happens at the wrong time or is not timed well.
Mistimed things can make people feel like something is not right or that things are not going as planned.
Examples:
The mistimed party started after everyone had already left.
She mistimed her jump and fell down.
The mistimed race ended before everyone was ready.
The mistimed joke made everyone laugh at the wrong time.
His mistimed arrival made everyone surprised.
The mistimed fireworks went off too early and scared everyone.