The Galactic Standard Calendar was established when humanity from Earth spread amongst the stars in all corners of the Milky Way galaxy. In order to establish a uniformity amongst all people that aligned with the GPOT-C and even those who did not, they established the Galactic Standard calendar. The calendar was based on Earth time located at the timezone of GMT 0. The calendar comprises of 365 days, a day consisting of 24 hours, a week being made up of 7 days and a month being made up of about 30 days, give or take a few depending on the month. There are 12 months making up a year. The months are January, February, March, April, May, June, July, August, September, October, November and December.
It is typical for space-faring people to keep at least three sets of times on their ships, those times being the local time on their planet based on where their timezones start, the local time where they primarily live or do their business, and the Galactic Standard time, which is based on what time it is on Earth at GMT 0 and the universal time that is used in the Milky Way.
Galactic Standard Time (GST) is the official time used in space.