What would a solar empire's calendar look like?

Question

Background information

Let's say that humanity somehow has colonized almost every celestial body in the solar system (with the exception of the gas giants, Venus and Mercury): we mine moons and asteroids, we live on planets, etc. There now exists a problem in keeping humanity united; the calendar. The Gregorian calendar used on Earth in no way slides nicely into the cycles of other bodies. The highest point in the solar empire has decided that a new calendar should be put into place and has hired the system's greatest minds to design it.

The Question

What would this new calendar look like? What would need to be done so that all the dates, day, week, month and year, all coincide with each other? Keep in mind that the calendar must be able to be read and understood in every area of the solar system.

Answer 1

Astronomers already use such a system: https://en.wikipedia.org/wiki/Julian_day

This is the system that the Federation's stardates are based on, in Star Trek.

Answer 2

They would simply use Earth years. “Years” farther out in the solar system are simply too long to serve as useful units of time—Pluto’s orbital period is nearly 250 years!

There is no need for people to synchronize years with physical characteristics of the celestial body they are on. I doubt anyone is using insolation to farm crops out on Mars. They would simply schedule things in terms of the old calendar.

Answer 3

Finally introducing the metric system to time calculations would be a great start. Hours, minutes and seconds will probably be left intact, but standardising of a year to be 10 months of 100 days of 10 hours each would really simplify calculations.

Ultimately, it depends on major economic factors. Our present calendar was designed around agricultural cycles, since that was the major time dependent agricultural activity. Everything else was mostly time independent, e.g., it really doesn't matter to the miller, weaver or smith when they work, except as it relates to the supply of grain or wool or coal and iron ore.

If Earth remains the major food producer, the present systems will remain intact. If food production is distributed across the system with various calendars, unless there's a major economic activity that relies on a specific timescale, it doesn't matter what rules you impose, much like daylight savings. Some people will be inconvenienced, others won't, some will benefit. Just try to avoid changing to the new rules during a major peak season.

Answer 4

Some kind of standardized astronomical time would be nice, basically a number that counts up from zero at a picosecond rate. People could track a range of digits starting from the 13th (a second), the new minute will be every 100 seconds so that's the 15th digit, the new hour every 100 new minutes which is the 17th digit, etc.

This kind of time keeping would be a lot more intuitive for comparing especially large and short periods of time, for example say a spaceship performs a course correction every tenth of a second, how many course corrections will occur in five years? With new time this is a lot easier to calculate because you don't need to convert tenths of a second into seconds, seconds into minutes, minutes into hours, hours into days, days into weeks/months/years, and account for leap years.