I seem to remember several dating systems mainly in the Star Wars Expanded Universe. Furthermore, I was wondering if periods of time such as seconds, days, or months represent the same amount of time as they do in the real world.

So these are the main points of this question:

  1. Which are the different dating systems (if there is indeed more than one) in the Star Wars galaxy? How are they related in regard to time offsets and such? (e.g. One system's year 5000 is another's year 268) An explanatory timeline graphic - perhaps including some important events - would be especially appreciated!

  2. Do amounts of time in the dating system(s) such as minutes or hours represent the same amount as in the real world? If more than one system exists, do the amounts of time carry over between them? (e.g. 1 minute is the same amount of time in all systems.)

  3. If the times carry over (or there is, in fact, only one system), what planet are the units of time based on? Coruscant?

Sorry if it seems I have asked too much in one question - splitting this question up into multiple questions did not appear to be a good idea as much of its content is very related.

Thanks for your time!

  • 1
    @genesis Could you specify your reason for removing everyone's thanks? IMO, "not necessary" does not help anyone understand what was removed and the cause for doing so. I feel like we should be allowed to thank others for the time they spend helping others find answers. Commented Oct 15, 2011 at 14:03
  • @genesis The Science Fiction and Fantasy site seems a bit more...I don't know..._friendly_ and easy-going than some of the other SE sites. That said, I see your point, but when you upvote answers, others can't tell who upvoted what. (Which makes "thanks" kind of impersonal, in my mind.) Commented Oct 15, 2011 at 15:35
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    @PeterDC This Meta.SO question addresses salutations. They're not considered appropriate for a number of reasons, and as per this answer are now even automatically removed from SO proper.
    – FAE
    Commented Oct 19, 2011 at 13:03
  • @FallenAngelEyes I find it interesting that you cite that question, as it is primarily focused on greetings. It also has many different opinions - and thanks being acceptable and polite is expressed in several of them. One person feels it's rude to thank complete strangers, another thinks it's rude not to. We all have our preferences. I happen to be in the (slightly less popular) latter group. If you're going to remove someone's expression of thanks, though, something more descriptive than "not necessary" should be used as an edit summary. Commented Oct 19, 2011 at 14:26

2 Answers 2

  1. Almost everything about Star Wars is based on the Galactic Standard Calendar which uses the Battle of Yavin as its epoch (year 0). There are various other epochs, for instance, the formation of the Galactic Empire. There is a comprehensive text timeline here
    • BBY stands for Before the Battle of Yavin, and ABY stands for After the Battle of Yavin. (The Battle of Yavin ended with the destruction of the first Death Star, or if you prefer, the end of Star Wars Episode IV: A New Hope).
  2. As for the time, there's nothing to indicate how it's related to earth's time, it just said that it's 24 hours = 1 day, 60 minutes = 1 hour, and 60 seconds = 1 minute.
    As for the calendar, it's slightly different from ours:
    • A standard week is 5 standard days
    • Each month is exactly seven weeks. (Making 35 standard days each month.)
    • A standard year was 368 days, and was composed of:
  3. Yes, Coruscant Solar cycle

The Galactic Standard Calendar was the standard measurement of time in the galaxy. It centered around the Coruscant Solar cycle, which was 368 days long (one day consisting of 24 standard hours). Numerous epochs were used to determine calendar eras. The most recent of these calendar eras used the Battle of Yavin as its epoch, or "year zero." BBY stands for Before the Battle of Yavin, and ABY stands for After the Battle of Yavin

  • 3
    So that's what BBY and ABY mean! Thanks for your (second?) quick (and helpful) answer! :) Commented Sep 21, 2011 at 16:11
  • 6
    Don't forget about everyone's favorite measure of time, parsecs.
    – Wooble
    Commented Sep 22, 2011 at 16:52
  • "...in under twelve parsecs..." ;) Commented Sep 22, 2011 at 19:17
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    Late coming to the party... is BBY and ABY in-universe? Seems odd the the Emperor would use one of his Empire's greatest failings as the basis of a new epoch.
    – Skooba
    Commented Apr 2, 2016 at 12:44
  • True and the old republic would have known nothing about it Commented Apr 2, 2016 at 13:05


In the new Disney canon, there are many dating systems, only two of which have been described:

  1. Leland Chee, a creative executive with Lucasfilm, noted on Twitter in late 2016 that one such calendar, used exclusively by Rebels, is the ABY/BBY system from Legends, which takes the climax of A New Hope as year 0:

    enter image description here

    @c_gibbs1000: Does the BBY and ABY year designations apply in 'Canon' as it did in 'Legends'? Much appreciated.

    @HolocronKeeper: It is one of many in-universe calendars. Out-of-universe, it makes more sense to use those years with the BSW4/ASW4 acronym.

    @HolocronKeeper: As to who would use it in-universe, it wouldn't be any non-Rebel and it couldn't be used before BY.

    He was asked the question again a few days later, and remarked that it wasn't a commonly-used system:

    enter image description here

    @JediSAS: Does/will official canon have a dating system the way Legends canon did (BBY/ABY)? [...] Crap, I forgot to specify that I'm wondering about an in-universe dating system. Oops.

    @HolocronKeeper: ABY/BBY is one of many. Few would actually use and accept that one as standard.

  2. The canon reference book Star Wars: Absolutely Everything You Need To Know reveals that the planet Lothal had its own calendar system. The only thing known about it is that the Empire was founded in 3258 LY:

    enter image description here

    This calendar is presumably based on the length of Lothal's orbit around its star; it's unknown how that relates to Coruscant's orbital period, so equating the two calendars is impossible.

    It's unknown whether Lothal retained this calendar throughout its Imperial history.


In an episode of Rebels Recon, a behind-the-scenes show for Star Wars Rebels, Pablo Hidalgo revealed that planets synchronize their timekeeping with Coruscant:

Andi Gutierrez: Nolan Jiminez asks: "How is time measured in the galaxy if each planet has a different time of rotation and translation?

Hidalgo: We kind of assume that there is a standard hour, a standard day, a standard month; a unit of measurement that everyone understands how long that is; and, in our storytelling, we say that all that measurement comes from Coruscant. So, not only is it the galactic capital, it's sort of the yardstick through which all time is measured in the galaxy.

Rebels Recon #2.09: Inside "The Future of the Force"

Per the canon reference book Star Wars: Absolutely Everything You Need To Know, a standard day is 24 standard hours, and a standard year is 365 standard days:

enter image description here

It's unknown how, or if, this would have changed after the collapse of the Empire, when Coruscant ceased to be the capital of the galaxy; it seems unlikely that something like this would change, but you never know.

  • According to @DavRob60's answer, Coruscant has 368 days. What happened to those three days? Did they lose ALL their holidays? Commented Dec 29, 2016 at 18:28
  • The 365-day year is confirmed onscreen in Andor S1E8: a character with a six-year prison sentence has a day counter that reads 2,189 (one day shy of six 365-day years).
    – Milo P
    Commented Nov 1, 2022 at 16:17

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