Dates That Don't Exist (2015)(blog.yossarian.net) |
Dates That Don't Exist (2015)(blog.yossarian.net) |
> In A.D. 1582 Pope Gregory XIII found that the existing Julian calendar insufficiently represented reality, and changed the rules about calculating leap years to account for this. Similarly, in A.D. 2013 Rockchip hardware engineers found that the new Gregorian calendar still contained flaws, and that the month of November should be counted up to 31 days instead.
In our Dip (in house db) client library, we built what we called a policy that auto selects partitions based on every crud operations. The policies can be specified once for each collection in collections.json based on fields or query.
So for policies where partition involves the date type fields, be it range or fixed dates, it was incredibly hard to generate universal date names from ranges.
The policy mechanism was finished fairly quickly as Dip is inherently distributed first. But reasoning about date names was so incredibly hard.
The missing dates mentioned in the article did come up during development adding to the woes.
But the upside now is that application code no longer worries about the distributed partitions. Policy handles that. Some sort of architecture as code. Don't know whether AAC is an existing term or whether we coined it.
Technically, they switched to the Revised Julian[0] calendar, not the Gregorian. Also, it was only some of the churches making up Eastern Orthodoxy that switched; others remain on the Julian calendar to this day, and all of them still use the Julian calendar to calculate the date of Pascha.
tl;dr - ActiveSupport::TimeWithZone used absolute seconds counting to determine dates while DateTime used a proper Gregorian calendar. This means dates before October 15, 1582 have different internal values when compared.
The behavior showed up because a test was using a DateTime value to set a MySQL DATETIME column to the DB minimum value, which is 1000-01-01 00:00:00, and then comparing the DB record attribute to the original variable used to set it.
Something like:
date = DateTime.new(1000, 1, 1, 0, 0, 0, 'UTC')
record.update(happened_at: date)
record.happened_at == date # => false
https://en.wikipedia.org/wiki/List_of_non-standard_dates#Feb...
Tried using ncal like in the examples in that blog post, but it did not work correctly using either Julian or Gregorian. Of course the Swedish calendar from 1700-1712 was neither, but somewhere in-between, because of the (failed) attempt to gradually move from one to the other.
Meta: one can also link to this article, which redirects:
imo, if i am using Georgian i want that system even retroactively, just like projecting a date back into the stone age. I don't care that a particular geography or culture changed calendars.
So I suppose what is really going on is that some libraries are using Georgian consistently, and others are using some hybrid "civic" calendar that tracks what the romans and the catholics were using, so dates in history books make sense.
It would natively display "Future" if the file timestamp was ahead of the system clock, but you could also add dates. I remember seeing directory listings like
xyzzy.foo 49152 ----rw-d Christmas 1988I’ll draft a Dubia so that when future popes change the calendar they will include a representative code sample and details about how we handle this.
(It’s important to remember that the pope and friends were operating much more like an international standards body than a religious leader when doing things like this.)
And if there is a contract dated to the 6th October 1582, that does raise questions about its legitimacy (though in general misdating a contract does not void it, it would merely be one point of evidence in your argument that it's a forgery, just like using a particular font in a modern printed contract)
'A date object represents a date (year, month and day) in an idealized calendar, the current Gregorian calendar indefinitely extended in both directions.'
'This matches the definition of the “proleptic Gregorian” calendar in Dershowitz and Reingold’s book Calendrical Calculations.'
https://docs.python.org/3/library/datetime.html#id2 https://docs.python.org/3/library/datetime.html#id5
Whereas Ruby has proleptic Gregorian Time, but civic DateTime:
https://ruby-doc.org/stdlib-2.6.1/libdoc/date/rdoc/DateTime....