Gregorian calendar

The Gregorian calendar was the calendar for the people of Earth and Luna, and until the Purge, was the most widely-used system of timekeeping among humanity. The other two competing systems were the Helios Calendar and the Arean calendar, as a standard timekeeping measure and a timekeeping system for Mars, respectively.

• Solar Storms Calendar Converter
• One modification to the calendar has been made. Every 4,000 years is considered to be a skip year, where a leap year is not counted, in order to bring the calendar closer in line with the mean tropical year.

Even before the 21st century, many attempts to reform the Terran calendar had been made. They all failed, as did further attempts through the 22nd century. The next winner would be a calendar that actually took the slowing of Earth's rotation into account, but the potential for human intervention made this somewhat suspect. The Solarian Purge effectively ended this calendar, as calculating for delta T meant that the only 'guaranteed' unit of time was the year. Adding in the concept of drift was also a bit much, and many stuck with the Helios calendar, sometimes using the Arean one to be odd.