Galactic Standard Calendar

The Galactic Standard Calendar is the standard measurement of time in the galaxy. It centered around the Battle of Yavin as the starting year. BBY stands for Before the Battle of Yavin, and ABY stands for After the Battle of Yavin. This calendar is based on the size and rotation of the planet Coruscant. It is a luno-solar calendar based both on Coruscant's orbit around its sun, and the orbit of its primary satellite Centrax 1. The standard unit of time is the standard second. Sixty standard seconds make up each standard minute, and sixty minutes make up each standard hour. Each day consists of 24 standard hours. A standard week is 5 standard days, and each month is seven weeks. (making 35 standard days each month) A standard year is 368 days, comprised of ten months, three fete weeks, and three holidays. As the Hyper-mechanics allows space travellers to bypass relativity, a single duration of time passes at all locations equally over a given interval.

History
The Calendar, formally known as the Galactic Standard Calendar, and also referred to as Coruscant Standard Calendar, was the main calendar in use in the galaxy since the time of the Galactic Republic. The Old Republic dated years from the Ruusan Reformation of 1,000 BBY. Prior to that, the Republic had dated events from it's founding in 25,000 BBY. The Empire used the same calendar, although they preferred to date events from the Great Resynchronization of 35 BBY, or from the Emperor Palpatine's ascension to the throne (19 BBY).

After the fracturing of the Empire, the New Republic reclaimed the calendar with Battle of Yavin as the starting year, it was by no means the most accepted calendar in the galaxy. It was used almost exclusively by the Rebel Alliance, the New Republic, and the Galactic Alliance. Many regions had their own calendar, including the Imperial Remnant.

Time Measurement
In the The Galaxy:


 * 368 days = 1 year
 * 60 minutes = 1 hour
 * 24 hours = 1 day
 * 5 days = 1 week
 * 7 weeks = 1 month
 * 35 days = 1 month
 * 10 months + 3 festival weeks + 3 holiday days = 1 year

The Tapani Sector's Year

 * By the Tapani Sector's domestic calendar, which is Galactic Standard with local names, the year flows as follows:
 * Month 1: Elona
 * Month 2: Kelona
 * Holiday 1: Tapani Day
 * Month 3: Selona
 * Festival Week 1: Expansion Week
 * Month 4: Telona
 * Month 5: Nelona
 * Holiday 2: Productivity Day
 * Month 6: Helona
 * Festival Week 2: Shelova Week
 * Month 7: Melona
 * Month 8: Yelona
 * Holiday 3: Harvest Day
 * Month 9: Relona (The Freeworlds Region of the Tapani Sector also recognizes Relona 10 - 15 as Independence Week.)
 * Month 10: Welona
 * Festival Week 3: Winter Fete

The Galactic Year

 * From the above information, we can extrapolate that the year, whether Tapani-named or not, in the galaxy flows as follows:
 * 2 months
 * 1 holiday
 * 1 month
 * 1 festival week
 * 2 months
 * 1 holiday
 * 1 month
 * 1 festival week
 * 2 months
 * 1 holiday
 * 2 months
 * 1 festival week

The week

 * The week flows as follows:
 * Day 1: Atunda
 * Day 2: Katunda
 * Day 3: Satunda
 * Day 4: Datunda
 * Day 5: Natunda

Behind the scenes
BBY/ABY is sometimes known as BSW4/ASW4, which means "before/after Star Wars Episode IV". The BSW4/ASW4 was used in the Essential Guide books, and has caught on a small following in Star Wars fandom, even though most fans use BBY/ABY.

When the Thrawn trilogy kicked off most of the work in the Expanded Universe, promotional material originally dated events in terms of the Battle of Endor, rather than the Battle of Yavin. This trailed off some time after the release of The Truce at Bakura.