The question involves measuring time. The choice of units and correct use of terms (sidereal) is very important.
Simple case: Use hours and reference to one spot on Earth, this will not coincide with illumination of Mars from the sun.
Real world: Sol was coined for the Martian solar day. The sol on which a lander touched down was designated "Sol 0," and each successive sol was numbered consecutively. The sol was divided into 24 Martian hours, which were in turn divided into 60 minutes per hour and 60 seconds per minute, just as on Earth.
Answer: the system stretches Earth's 24-60-60 clock to fit the longer Martian sol. Metric clock advocates have their work cut out for them.
Examples:
The rotational period of Mars (day) is 24.6229 (Earth) hours, or 24 hours, 37 minutes.
The orbital period of Mars (year) is a bit less than 687 (Earth) days.
Mathematics
The measurement of time independent of our solar system is relative to observations made with respect to periodic atomic events assumed constant since creation.