Misc #19096
closed[Question] Time with `-00:00` offset is in UTC
Description
It's a bit unexpected but
Time.new(2022, 1, 1, 0, 0, 0, "-00:00").utc?
# => true
But time with +00:00
or 0
offset is treated as not UTC time:
Time.new(2022, 1, 1, 0, 0, 0, "+00:00").utc? # => false
Time.new(2022, 1, 1, 0, 0, 0, 0).utc? # => false
Is it an intentional behaviour? In this case could you please clarify the reason why it works this way?
ruby -v
ruby 3.1.2p20 (2022-04-12 revision 4491bb740a)
Updated by andrykonchin (Andrew Konchin) about 2 years ago
- Description updated (diff)
Updated by sawa (Tsuyoshi Sawada) about 2 years ago
On my computer, which is set to JST (+0900), the three examples make no difference:
Time.new(2022, 1, 1, 0, 0, 0, "-00:00").utc? # => false
Updated by zverok (Victor Shepelev) about 2 years ago
On my computer (GMT+2, Europe/Kyiv timezone), the same behavior is reproducing since 3.1 (and on the current head).
[Time.new(2022, 1, 1, 0, 0, 0, "+00:00").utc?, Time.new(2022, 1, 1, 0, 0, 0, "-00:00").utc?]
# => [false, true]
Before that (2.7 and 3.0), both are false
.
I'll try to debug it later this week if nobody else does.
Updated by zverok (Victor Shepelev) about 2 years ago
Oh, it is actually deliberate, see #17544:
In RFC 3339, -00:00 is used for the time in UTC is known, but the offset to local time is unknown.
Updated by andrykonchin (Andrew Konchin) about 2 years ago
Indeed. But I assumed this feature only affects #strftime
's %-z
directive, not treating a time zone offset.
I've checked on Ruby 3.0.3 and -00:00
wasn't treated as UTC:
Time.new(2022, 1, 1, 0, 0, 0, "-00:00").zone
# => nil
Updated by andrykonchin (Andrew Konchin) about 2 years ago
- Description updated (diff)
Updated by andrykonchin (Andrew Konchin) almost 2 years ago
@zverok (Victor Shepelev) Thank you for pointing at the original ticket.
TBH I was waiting so long for some official confirmation because I haven't found any mentioning that https://bugs.ruby-lang.org/issues/17544 affects not only Time#strftime
method but also a way how utc offset
argument (in Time construction methods) is handled. Even added tests don't check this behaviour.
Updated by nobu (Nobuyoshi Nakada) almost 2 years ago
- Status changed from Open to Closed
It is git|296a2cab.
See also the related changesets.
Updated by andrykonchin (Andrew Konchin) almost 2 years ago
@nobu (Nobuyoshi Nakada) Thank you!
Updated by duerst (Martin Dürst) almost 2 years ago
I'm not sure whether and how much this is relevant, but please note that the Sedate WG in the IETF has a draft (https://www.ietf.org/archive/id/draft-ietf-sedate-datetime-extended-07.html, close to final) that updates RFC 3339 (https://www.rfc-editor.org/rfc/rfc3339). For details, please check https://www.ietf.org/archive/id/draft-ietf-sedate-datetime-extended-07.html#name-updating-rfc-3339.
Updated by nobu (Nobuyoshi Nakada) over 1 year ago
duerst (Martin Dürst) wrote in #note-10:
I'm not sure whether and how much this is relevant, but please note that the Sedate WG in the IETF has a draft (https://www.ietf.org/archive/id/draft-ietf-sedate-datetime-extended-07.html, close to final) that updates RFC 3339 (https://www.rfc-editor.org/rfc/rfc3339). For details, please check https://www.ietf.org/archive/id/draft-ietf-sedate-datetime-extended-07.html#name-updating-rfc-3339.
Thank you for the interesting information.
Although that draft seems not recommending use of -00:00
, but it also says
the present specification however does not formally deprecate this syntax.
at https://www.ietf.org/archive/id/draft-ietf-sedate-datetime-extended-07.html#section-2-6