Calculate the period of a Planet in another Star System

Time is relative, if you’re standing on earth it takes one day or 24 hours for earth to do a complete rotation in and out of our stars light, while we remain in orbit around our sun.
Earth’s full orbital period around our sun takes 365 earth days.
The earth's spin and orbit are effects of the gravitational pull, as of when our solar system was created.
If you were standing on another planet it would most likely have a different numerical day and year.
To estimate the rotational period or day of a planet in a different solar system you first need to convert the estimated nubmer of days that it takes the planet to orbit it's star into seconds.
Then you can use Newtion and Kepler's Equations to make an estimation of the stars mass by using a standard 24 hour day, then you take your estimated result and divide it by the actual mass. This will let you know roughly what your accuary in math was, and allow you to adjust your hours per day estimation by using mass/math accuracy calculations.