“Imperial Standard Time” or “Imperial Standard” is the name given to the chronology that every part of the colonised galaxy follows, a time reference that is the same regardless of where you are in the colonised worlds. “Local time” or “planetary time” follows the same structure, but is specific to that planet or body the colony is based upon.
The structure is the same for either Imperial Standard Time or Local/Planetary Time :
Seconds (and further subdivisions, with micro- and nano-)
Years (and then decades, centuries, millennia, etc.)
“BE” refers to “Before Empire” and “AE” refers to “After Empire”, with the years numbered in both directions (note : this has replaced all alternative calendars previously in use). The Empire referred to is the Red Empire of Mars, and the date it was announced by the Red, or First, or True Emperor. The Imperial Calendar is the name given to the recording system adopted by even post-Dissolution secessionist nations.
As the Imperial Calendar is based on Martian daily rotation, not Earths, there are some subtle differences –
The average length of a Martian sidereal day is 24 hours 37 minutes and 22.663 seconds Earth-time, so in the Imperial Calendar and in Imperial Standard Time this is the equivalent to one Imperial day.
The Martian year (its sidereal year) is not used to specify the number of months in Imperial Standard Time, as it remains at 12 months to a year.
Imperial Standard Time is counted as :
Seconds (based on Mars rotation, not Earth, so there is a slight variance – see above)
Minute (60 seconds to a minute)
Hours (60 minutes to an hour)
Day (24 hours to a day, split into three “shifts” of eight hours each, still called Morning, Afternoon, Night).
Week (eight days to a week, based loosely)
Month (four weeks to a month – or thirty-two days each)
Year (20 months to a year, the closest thing to a Martian rotation although not exactly)
Months, weeks and days are now numbered, so the second day of the third week in the first month is :
Day 2 of Week 3 in Month 1