Space Time

Assuming the human race will eventually migrate to space, how should we measure time in the future? Our current method of counting how many times the earth rotates and the time it takes to orbit the sun may not make much sense once we abandon our home planet and eventually colonize other planets and or pockets of space far removed from mother earth. It seems to me we should measure the time it takes for something with a constant speed to pass between 2 non-variable points. I believe light is a good object to measure since I believe it’s present in all habitable areas of space and has a constant speed. I’m not quite sure what the start and end points of its travel should be used to signify the passing of one unit of time. One suggestion from a friend was the distance between peaks of radio waves. It would have to be a significant number of radio waves measured by the speed of light to create a unit useful to time every day events like boiling an egg.