Galactic Standard Time

Galactic Standard time is the system of time followed by the entire galaxy when dealing with interplanetary matters. The fundamental unit is the Standard Second (GSs), which is defined as ten billion oscillations of a hydrogen atom when exposed to a middling-frequency microwave, this makes the ss only somewhat shorter than the Human second. For all practical timekeeping purposes, it might as well be the same length.

From the Standard Second, every step up in timekeeping (minutes, hours, days, months) is in multiples of ten.