blocks|key|308325|text|听起来你想要的东西大概是|type|unstyled|depth|inlineStyleRanges|entityRanges|data|308326|ActiveSupport::TimeZone.new('America/New_York').local_to_utc(t)|code-block|syntax|javascript|308327|这表示将此本地时间(使用区域)转换为utc。如果您设置了Time.zone，那么您当然可以|offset|length|style|CODE|308328|Time.zone.local_to_utc(t)|308329|这不会使用附加到t的时区-它假设它是您转换的时区的本地时区。|308330|这里需要注意的一个边缘情况是DST转换:您指定的本地时间可能不存在或可能不明确。|308331|entityMap^0|0|0|S|9|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|W|8|@$I|X|J|Y|K|L]]|9|@]|A|$]]|$1|M|3|N|5|D|7|Z|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|10|8|@]|9|@]|A|$]]|$1|Q|3|R|5|6|7|11|8|@]|9|@]|A|$]]|$1|S|3|-4|5|6|7|12|8|@]|9|@]|A|$]]]|T|$]]

Sounds like you want something along the lines of 

<pre><code>ActiveSupport::TimeZone.new('America/New_York').local_to_utc(t)
</code></pre>

This says convert this local time (using the zone) to utc. If you have <code>Time.zone</code> set then you can of course to

<pre><code>Time.zone.local_to_utc(t)
</code></pre>

This won't use the timezone attached to t - it assumes that it's local to the time zone you are converting from.

One edge case to guard against here is DST transitions: the local time you specify may not exist or may be ambiguous.

blocks|key|91243|text|您需要在转换后将时间偏移量添加到您的时间中。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|91244|最简单的方法是：|91245|t+=+Foo.start_time.in_time_zone("America/New_York")
t+-=+t.utc_offset|code-block|syntax|javascript|91246|我不确定您为什么要这样做，尽管实际使用构建时间的方式可能是最好的。我想一些关于为什么你需要转换时间和时区的背景知识会很有帮助。|91247|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|N|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|O|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|P|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

You need to add the time offset to your time after you convert it.

The easiest way to do this is:

<pre><code>t = Foo.start_time.in_time_zone("America/New_York")
t -= t.utc_offset
</code></pre>

I am not sure why you would want to do this, though it is probably best to actually work with times the way they are built. I guess some background on why you need to shift time and timezones would be helpful.

blocks|key|308419|text|实际上，我认为您需要在转换后减去偏移量，如下所示：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|308420|1.9.3p194+:042+>+utc_time+=+Time.now.utc
=>+2013-05-29+16:37:36+UTC
1.9.3p194+:043+>+local_time+=+utc_time.in_time_zone('America/New_York')
+=>+Wed,+29+May+2013+12:37:36+EDT+-04:00
1.9.3p194+:044+>+desired_time+=+local_time-local_time.utc_offset
+=>+Wed,+29+May+2013+16:37:36+EDT+-04:00+|code-block|syntax|javascript|308421|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Actually, I think you need to subtract the offset after you convert it, as in:

<pre><code>1.9.3p194 :042 &gt; utc_time = Time.now.utc
=&gt; 2013-05-29 16:37:36 UTC
1.9.3p194 :043 &gt; local_time = utc_time.in_time_zone('America/New_York')
 =&gt; Wed, 29 May 2013 12:37:36 EDT -04:00
1.9.3p194 :044 &gt; desired_time = local_time-local_time.utc_offset
 =&gt; Wed, 29 May 2013 16:37:36 EDT -04:00 
</code></pre>

blocks|key|308476|text|def+relative_time_in_time_zone(time,+zone)
+++DateTime.parse(time.strftime("%25d+%25b+%25Y+%25H:%25M:%25S+#{time.in_time_zone(zone).formatted_offset}"))
end|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|308477|我想出了一个快速的小函数来解决这个问题。如果有人有更有效的方法，请把它贴出来！|unstyled|308478|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|J|8|@]|9|@]|A|$]]|$1|G|3|-4|5|F|7|K|8|@]|9|@]|A|$]]]|H|$]]

<pre><code>def relative_time_in_time_zone(time, zone)
 DateTime.parse(time.strftime("%d %b %Y %H:%M:%S #{time.in_time_zone(zone).formatted_offset}"))
end
</code></pre>

Quick little function I came up with to solve the job. If someone has a more efficient way of doing this please post it!

blocks|key|308506|text|如果您正在使用Rails，下面是Eric+Walsh回答的另一种方法：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|308507|def+set_in_timezone(time,+zone)
++Time.use_zone(zone)+{+time.to_datetime.change(offset:+Time.zone.now.strftime("%25z"))+}
end|code-block|syntax|javascript|308508|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

If you're using Rails, here is another method along the lines of Eric Walsh's answer:

<pre><code>def set_in_timezone(time, zone)
 Time.use_zone(zone) { time.to_datetime.change(offset: Time.zone.now.strftime("%z")) }
end
</code></pre>

blocks|key|91462|text|我已经创建了几个助手方法，其中一个只做了Ruby+/+Rails+-+Change+the+timezone+of+a+Time,+without+changing+the+value上这篇文章的原始作者所要求的相同的事情。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|91463|此外，我还记录了一些我观察到的特性，并且这些helpers包含了完全忽略自动夏令时的方法，而时间转换在Rails框架中是不可用的：|91464|++def+utc_offset_of_given_time(time,+ignore_dst:+false)
++++#+Correcting+the+utc_offset+below
++++utc_offset+=+time.utc_offset

++++if+!!ignore_dst+&&+time.dst?
++++++utc_offset_ignoring_dst+=+utc_offset+-+3600+#+3600+seconds+=+1+hour
++++++utc_offset+=+utc_offset_ignoring_dst
++++end

++++utc_offset
++end

++def+utc_offset_of_given_time_ignoring_dst(time)
++++utc_offset_of_given_time(time,+ignore_dst:+true)
++end

++def+change_offset_in_given_time_to_given_utc_offset(time,+utc_offset)
++++formatted_utc_offset+=+ActiveSupport::TimeZone.seconds_to_utc_offset(utc_offset,+false)

++++#+change+method+accepts+:offset+option+only+on+DateTime+instances.
++++#+and+also+offset+option+works+only+when+given+formatted+utc_offset
++++#+like+-0500.+If+giving+it+number+of+seconds+like+-18000+it+is+not
++++#+taken+into+account.+This+is+not+mentioned+clearly+in+the+documentation
++++#+,+though.
++++#+Hence+the+conversion+to+DateTime+instance+first+using+to_datetime.
++++datetime_with_changed_offset+=+time.to_datetime.change(offset:+formatted_utc_offset)

++++Time.parse(datetime_with_changed_offset.to_s)
++end

++def+ignore_dst_in_given_time(time)
++++return+time+unless+time.dst?

++++utc_offset+=+time.utc_offset

++++if+utc_offset+<+0
++++++dst_ignored_time+=+time+-+1.hour
++++elsif+utc_offset+>+0
++++++dst_ignored_time+=+time+%2B+1.hour
++++end

++++utc_offset_ignoring_dst+=+utc_offset_of_given_time_ignoring_dst(time)

++++dst_ignored_time_with_corrected_offset+=
++++++change_offset_in_given_time_to_given_utc_offset(dst_ignored_time,+utc_offset_ignoring_dst)

++++#+A+special+case+for+time+in+timezones+observing+DST+and+which+are
++++#+ahead+of+UTC.+For+e.g.+Tehran+city+whose+timezone+is+Iran+Standard+Time
++++#+and+which+observes+DST+and+which+is+UTC+%2B03:30.+But+when+DST+is+active
++++#+it+becomes+UTC+%2B04:30.+Thus+when+a+IRDT+(Iran+Daylight+Saving+Time)
++++#+is+given+to+this+method+say+'05-04-2016+4:00pm'+then+this+will+convert
++++#+it+to+'05-04-2016+5:00pm'+and+update+its+offset+to+%2B0330+which+is+incorrect.
++++#+The+updated+UTC+offset+is+correct+but+the+hour+should+retain+as+4.
++++if+utc_offset+>+0
++++++dst_ignored_time_with_corrected_offset+-=+1.hour
++++end

++++dst_ignored_time_with_corrected_offset
++end|code-block|syntax|javascript|91465|在将上述方法包装在类或模块中后，可以在rails控制台或ruby脚本上尝试的示例：|91466|dd1+=+'05-04-2016+4:00pm'
dd2+=+'07-11-2016+4:00pm'

utc_zone+=+ActiveSupport::TimeZone['UTC']
est_zone+=+ActiveSupport::TimeZone['Eastern+Time+(US+&+Canada)']
tehran_zone+=+ActiveSupport::TimeZone['Tehran']

utc_dd1+=+utc_zone.parse(dd1)
est_dd1+=+est_zone.parse(dd1)
tehran_dd1+=+tehran_zone.parse(dd1)

utc_dd1.dst?
est_dd1.dst?
tehran_dd1.dst?

ignore_dst+=+true
utc_to_est_time+=+utc_dd1.in_time_zone(est_zone.name)
if+utc_to_est_time.dst?+&&+!!ignore_dst
++utc_to_est_time+=+ignore_dst_in_given_time(utc_to_est_time)
end

puts+utc_to_est_time|91467|希望这能有所帮助。|91468|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/q/16818180/936494^0|K|20|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@$A|Z|B|10|1|11]]|C|$]]|$1|D|3|E|5|6|7|12|8|@]|9|@]|C|$]]|$1|F|3|G|5|H|7|13|8|@]|9|@]|C|$I|J]]|$1|K|3|L|5|6|7|14|8|@]|9|@]|C|$]]|$1|M|3|N|5|H|7|15|8|@]|9|@]|C|$I|J]]|$1|O|3|P|5|6|7|16|8|@]|9|@]|C|$]]|$1|Q|3|-4|5|6|7|17|8|@]|9|@]|C|$]]]|R|$S|$5|T|U|V|C|$W|X]]]]

I have created few helper methods one of which just does the same thing as is asked by the original author of the post at <a href="https://stackoverflow.com/q/16818180/936494">Ruby / Rails - Change the timezone of a Time, without changing the value</a>. 

Also I have documented few peculiarities I observed and also these helpers contains methods to completely ignore automatic day-light savings applicable while time-conversions which is not available out-of-the-box in Rails framework:

<pre><code> def utc_offset_of_given_time(time, ignore_dst: false)
 # Correcting the utc_offset below
 utc_offset = time.utc_offset

 if !!ignore_dst &amp;&amp; time.dst?
 utc_offset_ignoring_dst = utc_offset - 3600 # 3600 seconds = 1 hour
 utc_offset = utc_offset_ignoring_dst
 end

 utc_offset
 end

 def utc_offset_of_given_time_ignoring_dst(time)
 utc_offset_of_given_time(time, ignore_dst: true)
 end

 def change_offset_in_given_time_to_given_utc_offset(time, utc_offset)
 formatted_utc_offset = ActiveSupport::TimeZone.seconds_to_utc_offset(utc_offset, false)

 # change method accepts :offset option only on DateTime instances.
 # and also offset option works only when given formatted utc_offset
 # like -0500. If giving it number of seconds like -18000 it is not
 # taken into account. This is not mentioned clearly in the documentation
 # , though.
 # Hence the conversion to DateTime instance first using to_datetime.
 datetime_with_changed_offset = time.to_datetime.change(offset: formatted_utc_offset)

 Time.parse(datetime_with_changed_offset.to_s)
 end

 def ignore_dst_in_given_time(time)
 return time unless time.dst?

 utc_offset = time.utc_offset

 if utc_offset &lt; 0
 dst_ignored_time = time - 1.hour
 elsif utc_offset &gt; 0
 dst_ignored_time = time + 1.hour
 end

 utc_offset_ignoring_dst = utc_offset_of_given_time_ignoring_dst(time)

 dst_ignored_time_with_corrected_offset =
 change_offset_in_given_time_to_given_utc_offset(dst_ignored_time, utc_offset_ignoring_dst)

 # A special case for time in timezones observing DST and which are
 # ahead of UTC. For e.g. Tehran city whose timezone is Iran Standard Time
 # and which observes DST and which is UTC +03:30. But when DST is active
 # it becomes UTC +04:30. Thus when a IRDT (Iran Daylight Saving Time)
 # is given to this method say '05-04-2016 4:00pm' then this will convert
 # it to '05-04-2016 5:00pm' and update its offset to +0330 which is incorrect.
 # The updated UTC offset is correct but the hour should retain as 4.
 if utc_offset &gt; 0
 dst_ignored_time_with_corrected_offset -= 1.hour
 end

 dst_ignored_time_with_corrected_offset
 end
</code></pre>

Examples which can be tried on rails console or a ruby script after wrapping the above methods in a class or module:

<pre><code>dd1 = '05-04-2016 4:00pm'
dd2 = '07-11-2016 4:00pm'

utc_zone = ActiveSupport::TimeZone['UTC']
est_zone = ActiveSupport::TimeZone['Eastern Time (US &amp; Canada)']
tehran_zone = ActiveSupport::TimeZone['Tehran']

utc_dd1 = utc_zone.parse(dd1)
est_dd1 = est_zone.parse(dd1)
tehran_dd1 = tehran_zone.parse(dd1)

utc_dd1.dst?
est_dd1.dst?
tehran_dd1.dst?

ignore_dst = true
utc_to_est_time = utc_dd1.in_time_zone(est_zone.name)
if utc_to_est_time.dst? &amp;&amp; !!ignore_dst
 utc_to_est_time = ignore_dst_in_given_time(utc_to_est_time)
end

puts utc_to_est_time
</code></pre>

Hope this helps.

blocks|key|91547|text|我也花了很长时间来处理TimeZones，在修补了Ruby1.9.3之后，我意识到在转换之前不需要转换成命名的时区符号：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|91548|my_time+=+Time.now
west_coast_time+=+my_time.in_time_zone(-8)+#+Pacific+Standard+Time
east_coast_time+=+my_time.in_time_zone(-5)+#+Eastern+Standard+Time|code-block|syntax|javascript|91549|这意味着您可以专注于首先在您想要的区域中设置适当的时间，按照您思考的方式进行设置(至少在我看来，我是这样划分的)，然后在结束时转换为您想要验证业务逻辑的区域。|91550|这也适用于Ruby+2.3.1。|91551|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|P|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

I spent significant time struggling with TimeZones as well, and after tinkering with Ruby 1.9.3 realized that you don't need to convert to a named timezone symbol before converting:

<pre><code>my_time = Time.now
west_coast_time = my_time.in_time_zone(-8) # Pacific Standard Time
east_coast_time = my_time.in_time_zone(-5) # Eastern Standard Time
</code></pre>

What this implies is that you can focus on getting the appropriate time setup first in the region you want, the way you would think about it (at least in my head I partition it this way), and then convert at the end to the zone you want to verify your business logic with.

This also works for Ruby 2.3.1.

blocks|key|91585|text|我刚刚遇到了同样的问题，下面是我要做的：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|91586|t+=+t.asctime.in_time_zone("America/New_York")|code-block|syntax|javascript|91587|这是documentation+on+asctime|offset|length|91588|entityMap|0|LINK|mutability|MUTABLE|url|https://ruby-doc.org/core-2.2.0/Time.html#method-i-asctime^0|0|0|2|O|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@$I|V|J|W|1|X]]|A|$]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|R]]]]

I've just faced the same problem and here is what I'm going to do:

<pre><code>t = t.asctime.in_time_zone("America/New_York")
</code></pre>

Here is the <a href="https://ruby-doc.org/core-2.2.0/Time.html#method-i-asctime" rel="noreferrer">documentation on asctime</a>

blocks|key|308647|text|下面是另一个版本，它比目前的答案更适合我：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|308648|now+=+Time.now
#+=>+2020-04-15+12:07:10+%2B0200
now.strftime("%25F+%25T.%25N").in_time_zone("Europe/London")
#+=>+Wed,+15+Apr+2020+12:07:10+BST+%2B01:00|code-block|syntax|javascript|308649|它使用"%25N“传递纳秒。如果你想要另一个精确度，see+this+strftime+reference。|offset|length|308650|entityMap|0|LINK|mutability|MUTABLE|url|https://learnandlearn.com/ruby-programming/ruby-reference/ruby-strftime-date-formats-strftime-method-with-explanation^0|0|0|O|R|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@$I|V|J|W|1|X]]|A|$]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|R]]]]

Here's another version that worked better for me than the current answers:

<pre><code>now = Time.now
# =&gt; 2020-04-15 12:07:10 +0200
now.strftime("%F %T.%N").in_time_zone("Europe/London")
# =&gt; Wed, 15 Apr 2020 12:07:10 BST +01:00
</code></pre>

It carries over nanoseconds using "%N". If you desire another precision, <a href="https://learnandlearn.com/ruby-programming/ruby-reference/ruby-strftime-date-formats-strftime-method-with-explanation" rel="nofollow noreferrer">see this strftime reference</a>.

blocks|key|91635|text|这对我来说效果很好|type|unstyled|depth|inlineStyleRanges|entityRanges|data|91636|date+=+'23/11/2020'
time+=+'08:00'
h,+m+=+time.split(':')
timezone+=+'Europe/London'

date.to_datetime.in_time_zone(timezone).change(hour:+h,+min:+m)|code-block|syntax|javascript|91637|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

This worked well for me
<pre><code>date = '23/11/2020'
time = '08:00'
h, m = time.split(':')
timezone = 'Europe/London'

date.to_datetime.in_time_zone(timezone).change(hour: h, min: m)
</code></pre>

I have a record <code>foo</code> in the database which has <code>:start_time</code> and <code>:timezone</code> attributes.

The <code>:start_time</code> is a Time in UTC - <code>2001-01-01 14:20:00</code>, for example.
The <code>:timezone</code> is a string - <code>America/New_York</code>, for example.

I want to create a new Time object with the value of <code>:start_time</code> but whose timezone is specified by <code>:timezone</code>. I do not want to load the <code>:start_time</code> and then convert to <code>:timezone</code>, because Rails will be clever and update the time from UTC to be consistent with that timezone.

Currently,

<pre><code>t = foo.start_time
=&gt; 2000-01-01 14:20:00 UTC
t.zone
=&gt; "UTC"
t.in_time_zone("America/New_York")
=&gt; Sat, 01 Jan 2000 09:20:00 EST -05:00
</code></pre>

Instead, I want to see

<pre><code>=&gt; Sat, 01 Jan 2000 14:20:00 EST -05:00
</code></pre>

ie. I want to do:

<pre><code>t
=&gt; 2000-01-01 14:20:00 UTC
t.zone = "America/New_York"
=&gt; "America/New_York"
t
=&gt; 2000-01-01 14:20:00 EST
</code></pre>

Ruby / Rails - Change the timezone of a Time, without changing the value

数据库

我在数据库中有一个具有:start_time和:timezone属性的记录foo。例如，:start_time是UTC - 2001-01-01 14:20:00中的时间。例如，:timezone是一个字符串- America/New_York。我想创建一个新的Time对象，其值为:start_time，但其时区由:t...

问Ruby / Rails -更改时间的时区，但不更改值
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