ext/date/date_core.c: [DOC] fold long paragraphs

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@ -9477,7 +9477,16 @@ Init_date_core(void)
### When should you use DateTime and when should you use Time? ### When should you use DateTime and when should you use Time?
It's a common misconception that [William Shakespeare][1] and [Miguel de Cervantes][2] died on the same day in history - so much so that UNESCO named April 23 as [World Book Day because of this fact][3]. However because England hadn't yet adopted [Gregorian Calendar Reform][4] (and wouldn't until [1752][5]) their deaths are actually 10 days apart. Since Ruby's `Time` class implements a [proleptic Gregorian calendar][6] and has no concept of calendar reform then there's no way to express this. This is where `DateTime` steps in: It's a common misconception that [William Shakespeare][1] and
[Miguel de Cervantes][2] died on the same day in history -
so much so that UNESCO named April 23 as [World Book Day
because of this fact][3].
However because England hadn't yet adopted [Gregorian Calendar
Reform][4] (and wouldn't until [1752][5]) their deaths are
actually 10 days apart. Since Ruby's `Time` class implements a
[proleptic Gregorian calendar][6] and has no concept of
calendar reform then there's no way to express this. This is
where `DateTime` steps in:
``` irb ``` irb
>> shakespeare = DateTime.iso8601('1616-04-23', Date::ENGLAND) >> shakespeare = DateTime.iso8601('1616-04-23', Date::ENGLAND)
@ -9486,7 +9495,8 @@ Init_date_core(void)
=> Sat, 23 Apr 1616 00:00:00 +0000 => Sat, 23 Apr 1616 00:00:00 +0000
``` ```
Already you can see something's weird - the days of the week are different, taking this further: Already you can see something's weird - the days of the week
are different, taking this further:
``` irb ``` irb
>> cervantes == shakespeare >> cervantes == shakespeare
@ -9495,14 +9505,21 @@ Init_date_core(void)
=> 10 => 10
``` ```
This shows that in fact they died 10 days apart (in reality 11 days since Cervantes died a day earlier but was buried on the 23rd). We can see the actual date of Shakespeare's death by using the `gregorian` method to convert it: This shows that in fact they died 10 days apart (in reality 11
days since Cervantes died a day earlier but was buried on the
23rd). We can see the actual date of Shakespeare's death by
using the `gregorian` method to convert it:
``` irb ``` irb
>> shakespeare.gregorian >> shakespeare.gregorian
=> Tue, 03 May 1616 00:00:00 +0000 => Tue, 03 May 1616 00:00:00 +0000
``` ```
So there's an argument that all the celebrations that take place on the 23rd April in Stratford-upon-Avon are actually the wrong date since England is now using the Gregorian calendar. You can see why when we transition across the reform date boundary: So there's an argument that all the celebrations that take
place on the 23rd April in Stratford-upon-Avon are actually
the wrong date since England is now using the Gregorian
calendar. You can see why when we transition across the reform
date boundary:
``` irb ``` irb
# start off with the anniversary of Shakespeare's birth in 1751 # start off with the anniversary of Shakespeare's birth in 1751
@ -9518,9 +9535,21 @@ Init_date_core(void)
=> Fri, 04 May 1753 00:00:00 +0000 => Fri, 04 May 1753 00:00:00 +0000
``` ```
As you can see, if we're accurately tracking the number of [solar years][9] since Shakespeare's birthday then the correct anniversary date would be the 4th May and not the 23rd April. As you can see, if we're accurately tracking the number of
[solar years][9] since Shakespeare's birthday then the correct
anniversary date would be the 4th May and not the 23rd April.
So when should use you use `DateTime` in Ruby and when should you use `Time`? Almost certainly you'll want to use `Time` since your app is probably dealing with current dates and times. However, if you need to deal with dates and times in a historical context you'll want to use `DateTime` to avoid making the same mistakes as UNESCO. If you also have to deal with timezones then best of luck - just bear in mind that you'll probably be dealing with [local solar times][7], since it wasn't until the 19th century that the introduction of the railways necessitated the need for [Standard Time][8] and eventually timezones. So when should use you use `DateTime` in Ruby and when should
you use `Time`? Almost certainly you'll want to use `Time`
since your app is probably dealing with current dates and
times. However, if you need to deal with dates and times in a
historical context you'll want to use `DateTime` to avoid
making the same mistakes as UNESCO. If you also have to deal
with timezones then best of luck - just bear in mind that
you'll probably be dealing with [local solar times][7], since
it wasn't until the 19th century that the introduction of the
railways necessitated the need for [Standard Time][8] and
eventually timezones.
[1]: http://en.wikipedia.org/wiki/William_Shakespeare [1]: http://en.wikipedia.org/wiki/William_Shakespeare
[2]: http://en.wikipedia.org/wiki/Miguel_de_Cervantes [2]: http://en.wikipedia.org/wiki/Miguel_de_Cervantes