[ruby-core:66071] [ruby-trunk - misc #10473] [Open] Date.to_datetime.to_time != Date.to_time

[ruby-core:66071] [ruby-trunk - misc #10473] [Open] Date.to_datetime.to_time != Date.to_time

[lojack44]

Issue #10473 has been reported by Jack Lowe.

----------------------------------------
misc #10473: Date.to_datetime.to_time != Date.to_time
https://bugs.ruby-lang.org/issues/10473

* Author: Jack Lowe
* Status: Open
* Priority: Normal
* Assignee: 
* Category: 
* Target version: 
----------------------------------------

Date.new(2014,1,1).to_datetime.to_time.utc.to_s
=> "2014-01-01 00:00:00 UTC"

Date.new(2014,1,1).to_time.utc.to_s
=> "2014-01-01 05:00:00 UTC"




-- 
https://bugs.ruby-lang.org/

[ruby-core:75653] [Ruby trunk Misc#10473] Date.to_datetime.to_time != Date.to_time

[spiketeika]

Issue #10473 has been updated by Kaneko Yuichiro.


`Date#to_time` interprets date as the local time zone.
But `Date#to_datetime` interprets date as UTC.

I think this incompatibility is a king of bug.
We have two ways to solve this incompatibility, to make both methods to interpret date as the local time zone,
or to interpret date UTC.

It is difficult to judge which is more natural or useful.
But I always interpret date as the local time zone in my daily life...


```diff
diff --git a/ext/date/date_core.c b/ext/date/date_core.c
index 3a10fcb..4cc3dc9 100644
--- a/ext/date/date_core.c
+++ b/ext/date/date_core.c
@@ -8520,35 +8520,7 @@ date_to_date(VALUE self)
 static VALUE
 date_to_datetime(VALUE self)
 {
-    get_d1a(self);
-
-    if (simple_dat_p(adat)) {
-       VALUE new = d_lite_s_alloc_simple(cDateTime);
-       {
-           get_d1b(new);
-           bdat->s = adat->s;
-           return new;
-       }
-    }
-    else {
-       VALUE new = d_lite_s_alloc_complex(cDateTime);
-       {
-           get_d1b(new);
-           bdat->c = adat->c;
-           bdat->c.df = 0;
-           RB_OBJ_WRITE(new, &bdat->c.sf, INT2FIX(0));
-#ifndef USE_PACK
-           bdat->c.hour = 0;
-           bdat->c.min = 0;
-           bdat->c.sec = 0;
-#else
-           bdat->c.pc = PACK5(EX_MON(adat->c.pc), EX_MDAY(adat->c.pc),
-                              0, 0, 0);
-           bdat->c.flags |= HAVE_DF | HAVE_TIME;
-#endif
-           return new;
-       }
-    }
+    return time_to_datetime(date_to_time(self));
 }

 /*
diff --git a/test/date/test_date_conv.rb b/test/date/test_date_conv.rb
index 3729476..0feaf2a 100644
--- a/test/date/test_date_conv.rb
+++ b/test/date/test_date_conv.rb
@@ -126,10 +126,13 @@ def test_to_datetime__from_time

   def test_to_datetime__from_date
     d = Date.new(2004, 9, 19) + 1.to_r/2
-    d2 = d.to_datetime
-    assert_equal([2004, 9, 19, 0, 0, 0, 0, 0],
-                [d2.year, d2.mon, d2.mday, d2.hour, d2.min, d2.sec,
-                 d2.sec_fraction, d2.offset])
+
+    with_tz('Asia/Tokyo') do
+      d2 = d.to_datetime
+      assert_equal([2004, 9, 19, 0, 0, 0, 0, (3.to_r/8)],
+       [d2.year, d2.mon, d2.mday, d2.hour, d2.min, d2.sec,
+        d2.sec_fraction, d2.offset])
+    end
   end

   def test_to_datetime__from_datetime
```

----------------------------------------
Misc #10473: Date.to_datetime.to_time != Date.to_time
https://bugs.ruby-lang.org/issues/10473#change-58786

* Author: Jack Lowe
* Status: Open
* Priority: Normal
* Assignee: 
----------------------------------------

Date.new(2014,1,1).to_datetime.to_time.utc.to_s
=> "2014-01-01 00:00:00 UTC"

Date.new(2014,1,1).to_time.utc.to_s
=> "2014-01-01 05:00:00 UTC"




-- 
https://bugs.ruby-lang.org/

[ruby-core:75988] [Ruby trunk Misc#10473] Date.to_datetime.to_time != Date.to_time

[akr]

Issue #10473 has been updated by Akira Tanaka.


The proposed patch seems fine.

However I recommend to add more tests for old dates around transition between Jurian to Geregorian Calendar.

----------------------------------------
Misc #10473: Date.to_datetime.to_time != Date.to_time
https://bugs.ruby-lang.org/issues/10473#change-59182

* Author: Jack Lowe
* Status: Open
* Priority: Normal
* Assignee: 
----------------------------------------

Date.new(2014,1,1).to_datetime.to_time.utc.to_s
=> "2014-01-01 00:00:00 UTC"

Date.new(2014,1,1).to_time.utc.to_s
=> "2014-01-01 05:00:00 UTC"




-- 
https://bugs.ruby-lang.org/

[ruby-core:75992] [Ruby trunk Misc#10473] Date.to_datetime.to_time != Date.to_time

[akr]

Issue #10473 has been updated by Akira Tanaka.


Akira Tanaka wrote:
> The proposed patch seems fine.
> 
> However I recommend to add more tests for old dates around transition between Jurian to Geregorian Calendar.

I found that there are days that exists on Jurian carendar but not on Gregorian calendar.

1000/2/29 is exist on Jurian calender but it is not exist on Gregorian calendar.

So, Date.new(1000, 2, 29) preveserves the arguments but Time.new(1000, 2, 29) doesn't.

```
% ruby -rdate -e '
p Date.new(1000, 2, 29) 
p Time.new(1000, 2, 29)
'
#<Date: 1000-02-29 ((2086367j,0s,0n),+0s,2299161j)>
1000-03-01 00:00:00 +0918
```

So, Date.new(1000, 2, 29).to_time.to_datetime doesn't preserve the arguments
(and Date.new(1000, 2, 29).to_time.to_datetime.to_date doesn't round trip).

```
% ruby -rdate -e '
d = Date.new(1000, 2, 29)
p d
p d.to_time
p d.to_time.to_datetime  
p d.to_time.to_datetime.to_date
'
#<Date: 1000-02-29 ((2086367j,0s,0n),+0s,2299161j)>
1000-03-01 00:00:00 +0918
#<DateTime: 1000-03-01T00:00:00+09:18 ((2086367j,52861s,0n),+33539s,2299161j)>
#<Date: 1000-03-01 ((2086368j,0s,0n),+0s,2299161j)>
```


----------------------------------------
Misc #10473: Date.to_datetime.to_time != Date.to_time
https://bugs.ruby-lang.org/issues/10473#change-59192

* Author: Jack Lowe
* Status: Open
* Priority: Normal
* Assignee: 
----------------------------------------

Date.new(2014,1,1).to_datetime.to_time.utc.to_s
=> "2014-01-01 00:00:00 UTC"

Date.new(2014,1,1).to_time.utc.to_s
=> "2014-01-01 05:00:00 UTC"




-- 
https://bugs.ruby-lang.org/

[ruby-core:75994] [Ruby trunk Misc#10473] Date.to_datetime.to_time != Date.to_time

[akr]

Issue #10473 has been updated by Akira Tanaka.


Similar problem exists on Samoa (Pacific/Apia).

There is no 2011-12-30 in Pacific/Apia.
http://en.wikipedia.org/wiki/International_Date_Line

So, Date.new(2011,12,30) preserves the arguments but Time.new(2011,12,30) doesn't.

```
% TZ=Pacific/Apia ruby -rdate -e 'p Date.new(2011,12,30), Time.new(2011,12,30)'
#<Date: 2011-12-30 ((2455926j,0s,0n),+0s,2299161j)>
2011-12-31 00:00:00 +1400
```

Date doesn't depend on Time as much as possible.
In this sense, the current behavior, Date#to_datetime chooses UTC, is reasonable.

But if it is too confusing and Date#to_datetime should respect the local time zone
using Time, it is better to use only utc_offset as follows instead of the cascading
conversion date.to_time.to_datetime.

```
% TZ=Pacific/Apia ruby -rdate -e '
class Date
  def to_datetime2
    DateTime.new(year, mon, mday, 0, 0, 0, Time.new(year, mon, mday).utc_offset/86400r, start)
  end
end
d = Date.new(2011,12,30)
p d.to_datetime2'
#<DateTime: 2011-12-30T00:00:00+14:00 ((2455925j,36000s,0n),+50400s,2299161j)>
```


----------------------------------------
Misc #10473: Date.to_datetime.to_time != Date.to_time
https://bugs.ruby-lang.org/issues/10473#change-59194

* Author: Jack Lowe
* Status: Open
* Priority: Normal
* Assignee: 
----------------------------------------

Date.new(2014,1,1).to_datetime.to_time.utc.to_s
=> "2014-01-01 00:00:00 UTC"

Date.new(2014,1,1).to_time.utc.to_s
=> "2014-01-01 05:00:00 UTC"




-- 
https://bugs.ruby-lang.org/