3 ms·
A glitch in February of the year 0
- stymaar 3mo agoThe glitch starts with the existence of “year 0”: there's no such thing in the Christian calendars, it goes straight from 1BC to 1AD. (Zero didn't even exist in the 6th century when the Anno Domini epoch was set).
- astrobe_ 3mo agoAnd that's also why we are in the 21st century, not the 20th.
- stymaar 3mo agoArr[0] is the first element of an array, not the “zeroth”.
- keyle 3mo agoBut Arr could be empty or uninitialised...
- Perenti 3mo agoIn a zero based array type language. In pascal I believe arrays can start where you want them to as in "array[-10..10] of integer". It's been a while though. There is no year zero. Trying to compute with one is almost certainly an error. Trying to work with it is like dividing by zero - it does not make sense. The year "1" was originally a Julian Date. Using a Gregorian Date before the calendar was introduced is almost certainly an error. For ancient things, use Before Present, where I believe Present is defined to be sometime in 1950 or there about. For "modern" things (varying definitions of modern) use a sensible format/calendar that works in your database.
- astrobe_ 3mo ago> Using a Gregorian Date before the calendar was introduced is almost certainly an error. It's just an extrapolation; using the calendar being used at the considered time would be meaningless for us, e.g. the short-lived french republican calendar [1]. [1] https://en.wikipedia.org/wiki/French_Republican_calendar https://en.wikipedia.org/wiki/French_Republican_calendar
- quietbritishjim 3mo agoIf there was a year 0, we would still be in the 21st century. It would just have started 1 year earlier, in 2000 instead of 2001: 0 – 99: 1st century 100 – 199: 2nd century ... 1900 – 1999: 20th century 2000 – 2999: 21st century Although I think centuries are usually treated as starting in years ending in 0 anyway, in casual settings. Most people were certainly happy to celebrate "the new millennium" at the start of the year 2000.
- dcuthbertson 3mo ago> 2000 - 2999: 21st century You have the right idea, but you made the 21st century a millennium
- quietbritishjim 3mo agoArgh! I knew I'd make a stupid mistake like that. (Now too late to edit.)
- samlinnfer 3mo agoThey're just using astronomical year numbering.
- quink 3mo agoThey acknowledge that in the article, and make it clear that it really refers to 1 BC.
- GoblinSlayer 3mo agoFirst year is actually zeroth, just shifted by one. Calculations start with zear.
- shakna 3mo ago> Second, in the proleptic Gregorian calendar with astronomical year numbering (which is the calendar that we use on 28times), Non-Julian calendar.
- bazoom42 3mo agoThe article refers to the astronomical calendar, which is differnent from the gregorian by having a year 0, which makes calculations simpler. After year 1 the years have the same numbers, but before 1 they are off-by-one. Years before 0 is indicated with negative numbers, e.g -50 corresponds to 51 b.c.
- XYen0n 3mo ago> The first century starts at 0001-01-01 00:00:00 AD, although they did not know it at the time. This definition applies to all Gregorian calendar countries. There is no century number 0, you go from -1 century to 1 century. If you disagree with this, please write your complaint to: Pope, Cathedral Saint-Peter of Roma, Vatican. https://www.postgresql.org/docs/9.0/functions-datetime.html#FUNCTIONS-DATETIME-EXTRACT https://www.postgresql.org/docs/9.0/functions-datetime.html#...
- benj111 3mo ago00:00:00? Surely 12:00:00 or 24:00:00?
- throw1234567891 3mo ago00:00:00, there is no time such as 24:00:00. There could be 23:59:59, then 00:00:00.
- ButlerianJihad 3mo agoIt may surprise you or the PGSQL devs to learn that St. Peter's Basilica is not a cathedral at all! And while Vatican City is surrounded and enclosed by the city of Rome, you shouldn't need to put "Roma" in an address if it's destined for the sovereign nation of Vatican City. Your mail may arrive despite the silly addressing, but church buildings are not actually the places with mailboxes and postal routes. Okay, okay, it's a joke! I get it!
- ralferoo 3mo agoTheir implementation must surely be wrong anyway (caveat: I've not looked at the code) if they're worrying about leap years for year 0 / 1BC. Leap years didn't exist prior to AD 45, and then leap centuries were added from 1600 onwards (and 11 days missed out in 1582 to compensate for the leap years that were added on centuries that shouldn't have had the extra day added). If the astronomical calendar is the same as Gregorian all the way to year 1, then it must handle those rules the same as the Gregorian calendar, so there shouldn't be any leap years prior to AD 45 at all. Although that said, the month lengths were different before AD45 and there was sometimes an additional month inserted to realign the months and seasons. So trying to apply Gregorian calendar rules prior to AD45 seems a bit of a fool's errand anyway. If the astronomical calendar is used to make calculations easier (e.g. replacing 1BC with 0 and 2BC with -1), I'm not sure that they'd go to the effort of trying to insert additional months before AD45 just to line up with the Gregorian calendar (which it doesn't before AD1 anyway), so it'd make sense to simply use our current months and not apply any leap year logic prior to AD45 and just not worry about attempting to line up any dates prior to AD45 in the calendars at all. And of course, any historical documents prior to the fifth century would have been using a different calendar system for the years anyway, and would have to have been converted to AD or BC, so there's even less reason to worry about trying to make the dates in their calendar match up with the same exact dates with the modern calendars.
- mcphage 3mo agoYeah, it seems strange to get this "working", because fundamentally there is no correct answer. Our calendar isn't well defined in any consistent fashion back to then.
- lukasgelbmann 3mo agoAuthor here. Our aim isn’t to try and line up with the calendar that was in use at the time, 2026 years ago. Instead, the aim (for 28times) is to implement the rules of the proleptic Gregorian calendar[0] correctly. The bug was that those rules weren’t followed for some rare values. But to address your comment properly, I think I should justify why on Earth someone would want to use the proleptic Gregorian calendar for year 0 and before. In short, because it’s a useful fiction. The biggest reason is interoperability: a lot of software follows proleptic Gregorian rules, aligning around ISO 8601. Probably a clear majority of date/time software. We want to line up with all that existing software that assigns a specific meaning to a string like "0000-02-01". That’s the first of February in the proleptic Gregorian calendar, even though it was a different date in the ancient Romans’ calendar. The other reason is to keep it simple: since most people use the Gregorian calendar in present times, it’s simplest (for us as implementors, but also for users) to extend its rules into the distant past and distant future. The alternative for be to have multiple sets of rules, e.g. Julian and Gregorian calendar. (You might say it would be even simpler to just not allow timestamps before 1582. But there are use cases, e.g. in astronomy or history, where people want to work with timestamps before 1582, and even before 1 AD.) [0] https://en.wikipedia.org/wiki/Proleptic_Gregorian_calendar https://en.wikipedia.org/wiki/Proleptic_Gregorian_calendar
- pridy 3mo agoA bit off topic, but can someone give his opinion on the following question: is the webpage 28times.com from where the blog post is made with FastAPI? Building one myself and I am curious on this.