A Martian day is 39 minutes and 35 seconds longer than an Earth day. To distinguish the two, we use the term “sol” when referring to a Martian day.
Landers we have sent to Mars use special 24 hour clocks with longer seconds than those of Earth, so that a sol is divided into 24 periods, just like on Earth. The operations teams for these landers work and live by the same clocks. This means, for people working on these crews, their schedule shifts 40 minutes later each day. This makes for interesting problems.
