The standard of Universal Time (also known as EVE Standard Time) is the scientific measure of time used throughout New Eden. It is a relatively recent invention, having been agreed upon during the Yoiul Conference. The official time is kept on board the SCC headquarters station in Yulai, using a high precision atomic clock.
Even prior to the Yoiul Conference, all races throughout New Eden used the same basic units of measurement for time. A second was generally the smallest unit in every-day usage, with 60 seconds making up one minute. That is where the similarities ended, however, as each race divided their days into a different numbers of hours based on the rotation period of their home world, and then divided the hours into equal numbers of minutes. Similarly, months and years were divided unequally based on orbital period, seasonal changes, and local convention.
The current, widely-used calendar as mandated by interstellar treaty calls for 60 minutes to compose an hour, a single day to be constructed of 24 hours, a week to consist of 7 days, and a year to be comprised of 365 days. There are 12 months within a year, each containing between 28 and 31 days.
Prior to the Yoiul Conference, each empire used its own time-keeping method, typically based off the rotation and orbital period of their home planet. This obviously caused much confusion in trade, travel, and other enterprises, prompting the creation of one single calendar to the top of the agenda in peace negotiations.
Three different methods of time-keeping were established. The Arithmetics wanted to use a calendar based off mathematical measurements of the galaxy's rotation, with even the second redefined into scientific notational standards. The 25ers pointed to (now discredited) studies of the human internal clock which said a 25-hour day was most optimal. The final group, the Traditionalists, wished to use historical calendars they claimed were based on early settlements throughout New Eden.
In the end, it was the Traditionalists who prevailed, thanks to their strategy of lobbying politicians directly. The calendar proposed was reconstructed from fragmentary data recovered from early records, such as the Amarr Scriptures and information provided by the Jove. This decision was not without controversy, though later studies of the human biological clock proved that it matched the 24-hour cycle neatly.
After the establishment of Universal Time, the recording of years was begun at YC 0. Years prior to YC 0 traditionally count down from 23236 AD, based on extrapolation from old records used to construct the current calendar. A recent scientific push has called for dates prior to YC 0 to either count into negatives (ie. YC -10) or to count backwards using BYC as the notation (ie. BYC 10). However, no public traction has been gained to adjust the laws already in place.
While Universal Time is ubiquitous for space-based operations, particularly for capsuleers and interstellar trade, inhabited planets, especially those with little external contact, typically base their calendars on old methods. Some space stations in orbit around planets make use of the planet's calendar in additional to Universal Time to easily facilitate travel and trade.
Each empire also continues to maintain their old calendars, primarily for historical and traditional reasons. These calendars are primarily used for religious holidays; the Amarr staunchly follow the calendar laid out in the Scriptures for religious observances, for example. Conversely, the Minmatar have mostly adopted Universal Time for reckoning the dates of their tribal rituals.