The calendar, also referred to as the Coruscant Standard Calendar, was the main calendar in use in the galaxy since the time of the Galactic Republic. Presumably the Old Republic dated years from its founding in 25,053 BBY. Throughout time, however, historians have used numerous galaxy changing events as epoch to mark new calendar eras.
One particularly notable epoch is the Treaty of Coruscant of 3653 BBY. The calendar eras before and after this event (referred to as "BTC" and "ATC", respectively) were popularized by the famous Jedi historian Gnost-Dural. His holographic records, which used this numbering system, contained some of the most complete records of numerous important events such as the Hundred-Year Darkness, the Great Hyperspace War, the Great Sith War, the Mandalorian Wars, the Jedi Civil War, and the Great Galactic War against the returned Sith Empire. For this reason, this method of numbering years remains important to historians.
Other notable epochs used were the Ruusan Reformation of 1000 BBY, the Great ReSynchronization of 35 BBY, the formation of the Galactic Empire in 19 BBY, and the Battle of Endor in 4 ABY. With the exception of the Ruusan Reformation, the later epochs were all within the same century and stemmed from the events and upheavals surrounding the rise and fall of the Galactic Empire. They were short-lived and used by various historians at the time. In 25 ABY, the New Republic commissioned the New Republic Historical Council to re-standardize the Galactic Calendar. The historical council chose the Battle of Yavin, instead of the Battle of Endor, calling the former the more significant galactic event. From that point on, the year in which the Battle of Yavin occurred was the epoch used for the dating system. It was used by the New Republic, as well as the subsequent Galactic Alliance. Many regions, however, kept their own calendars, including the Imperial Remnant.
The calendar was based on the size and rotation of the planet Coruscant. It was a luno-solar calendar based both on Coruscant's orbit around its sun, and the orbit of its primary satellite Centax-1. The standard unit of time was the standard second. Sixty standard seconds made up each standard minute, and sixty minutes made up each standard hour. Each day consisted of 24 standard hours. A standard week was 5 standard days, and each month was seven weeks (making 35 standard days each month). A standard year was 368 days, composed of ten months, three fete weeks, and three holidays. As the Hyperdrive Theory allowed space travelers to bypass relativity, a single duration of time passed at all locations equally over a given interval.
In the galaxy:
- 60 seconds = 1 minute
- 60 minutes = 1 hour
- 24 hours = 1 day
- 5 days = 1 week
- 7 weeks = 1 month
- 35 days = 1 month
- 368 days = 1 year
- 10 months + 3 festival weeks + 3 holidays = 1 year
- Centaxday (Centaxday is similarly named to the real-life Monday, both connected with moons.)
- Taungsday (It was named for the Taungs of Coruscant.)
- Zhellday (It was named for the Zhell of Coruscant, presumably Humans ancestor)
- Benduday (It shared its name with the Bendu monks and the Bendu symbol of the Galactic Republic. )
New Year Fete Week was the first five days of the new year as determined by the Galactic Standard Calendar, but before the first month.
The Festival of Life, which originated in the Core Worlds, consisted of five days between the sixth and seventh months. It was marked by parties, get-togethers, and gift-giving.
The Festival of Stars was another celebratory week between the ninth and tenth months of the year that celebrates interstellar space travel. Many beings took vacations to other planets to mark this occasion.
The festivities concluded with the Galactic Fair (Imperial Fair during the Galactic Empire). Information on the Remnant's celebration of these weeks or the holidays is yet to be determined.