You could store the number of milliseconds since an arbitrary date in Greenwich UK, and provide methods to get the time, but even this has problems. The units

You could store the number of milliseconds since an arbitrary date in Greenwich UK, and provide methods to get the time, but even this has problems. The units could be defined by atomic vibrations or by the spinning of a large celestial object but these don’t agree. What is more the large celestial object (and others nearby) distorts space and time adding to the issue of where the time is (see my past submission on Barycentric Time)