I would like to create a Time/DateTime object that always represents "8am in New York", regardless of DST. How can i achieve this ?
One suggestion in the Rails documentation was to use
Time.zone = 'Eastern Time (US & Canada)'
in the following manner
around_filter :set_time_zone
def set_time_zone
if logged_in?
Time.use_zone(current_user.time_zone) { yield }
else
yield
end
end
But i would like to avoid touching thread variables (which is what Time.use_zone is doing)
Try this:
ActiveSupport::TimeZone['Eastern Time (US & Canada)'].parse('8:00')
That will handle day light savings time issues
> eight_am = ActiveSupport::TimeZone['Eastern Time (US & Canada)'].parse('8:00')
=> Fri, 22 May 2015 08:00:00 EDT -04:00
> eight_am.in_time_zone('America/Los_Angeles')
=> Fri, 22 May 2015 05:00:00 PDT -07:00
Well, you could approach the problem this way:
ny = Time.new(Time.now.year,Time.now.month,Time.now.day,8,0,0,"-05:00")
This will return an object ny that is set for 8:00 AM EST (New York) for the current day on any day that you execute it.
I am trying to have my validation prevent a user from creating an Appointment that is not in the future. My validation is working to prevent past appointments from being created, but it is also preventing the user from creating appointments today, which should be allowed. What is wrong here?
Appointment.rb:
validates :pickuptime, presence: true
validate :pickuptime_is_in_future
byebug
def pickuptime_is_in_future
if pickuptime < Time.now
errors.add(:pickuptime, "Appointment must be in the future")
end
end
I debugged this (using byebug), and at the point where the byebug line is, I found the following:
(byebug) Time.now
2014-12-20 20:33:35 -0500
(byebug) pickuptime
Sat, 20 Dec 2014 21:34:00 UTC +00:00
(byebug) pickuptime < Time.now
true
Why is this true if Time.now is 8:33pm and pickuptime is 9:34 pm?
Any help would be much appreciated, thanks!
TlDR;
Your Time Zone is not set.
A list of all available Time Zones can be fetched using
rake time:zones:all
and Set your timezone.
# application.rb:
class Application < Rails::Application
config.time_zone = 'Eastern Time (US & Canada)'
end
Long Answer
You are seeing a difference because of Time Zones and your local system UTC Offset.
(byebug) Time.now
2014-12-20 20:33:35 -0500
This Time is -05:00 hours or 5 hours behind UTC
(byebug) pickuptime
Sat, 20 Dec 2014 21:34:00 UTC +00:00
This Time is 00:00 hours or 0 hours behind UTC
(byebug) pickuptime < Time.now
true
Therefore this is true because your local time is actually
Sun, 21 Dec 2014 01:33:35 UTC +00:00
and the pickuptime is
Sat, 20 Dec 2014 21:34:00 UTC +00:00
and happens because your Time Zone is not set. To do so follow below.
A list of all available Time Zones can be fetched using
rake time:zones:all
and set your timezone. As detailed in ActiveSupport::TimeZone
# application.rb:
class Application < Rails::Application
config.time_zone = 'Eastern Time (US & Canada)'
end
I have a date stored in UTC in my Rails app and am trying to display it to a user who has "Eastern Time (US & Canada)" as their timezone. The problem is that rails keeps converting it to Eastern Daylight Time (EDT) so midnight is being displayed as 8am when it should be 7am. Is there anyway to prevent the DST conversion?
>> time = DateTime.parse("2013-08-26T00:00:00Z")
=> Mon, 26 Aug 2013 00:00:00 +0000
>> time.in_time_zone("Eastern Time (US & Canada)")
=> Sun, 25 Aug 2013 20:00:00 EDT -04:00
Update
I eventually went with a twist on #zeantsoi 's approach. I'm not a huge fan of adding too many rails helpers so I extended active support's TimeWithZone class.
class ActiveSupport::TimeWithZone
def no_dst
if self.dst?
self - 1.hour
else
self
end
end
end
Now I can do time.in_time_zone("Eastern Time (US & Canada)").no_dst
Create a helper that utilizes the dst? method on TimeZone to check whether the passed timezone is currently in DST. If it is, then subtract an hour from the supplied DateTime instance:
# helper function
module TimeConversion
def no_dst(datetime, timezone)
Time.zone = timezone
if Time.zone.now.dst?
return datetime - 1.hour
end
return datetime
end
end
Then, render the adjusted (or non-adjusted) time in your view:
# in your view
<%= no_dst(DateTime.parse("2013-08-26T00:00:00Z"), 'Eastern Time (US & Canada)') %>
#=> Sun, 25 Aug 2013 19:00:00 EDT -04:00
I have a record foo in the database which has :start_time and :timezone attributes.
The :start_time is a Time in UTC - 2001-01-01 14:20:00, for example.
The :timezone is a string - America/New_York, for example.
I want to create a new Time object with the value of :start_time but whose timezone is specified by :timezone. I do not want to load the :start_time and then convert to :timezone, because Rails will be clever and update the time from UTC to be consistent with that timezone.
Currently,
t = foo.start_time
=> 2000-01-01 14:20:00 UTC
t.zone
=> "UTC"
t.in_time_zone("America/New_York")
=> Sat, 01 Jan 2000 09:20:00 EST -05:00
Instead, I want to see
=> Sat, 01 Jan 2000 14:20:00 EST -05:00
ie. I want to do:
t
=> 2000-01-01 14:20:00 UTC
t.zone = "America/New_York"
=> "America/New_York"
t
=> 2000-01-01 14:20:00 EST
Sounds like you want something along the lines of
ActiveSupport::TimeZone.new('America/New_York').local_to_utc(t)
This says convert this local time (using the zone) to utc. If you have Time.zone set then you can of course to
Time.zone.local_to_utc(t)
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.
I've just faced the same problem and here is what I'm going to do:
t = t.asctime.in_time_zone("America/New_York")
Here is the documentation on asctime
If you're using Rails, here is another method along the lines of Eric Walsh's answer:
def set_in_timezone(time, zone)
Time.use_zone(zone) { time.to_datetime.change(offset: Time.zone.now.strftime("%z")) }
end
You need to add the time offset to your time after you convert it.
The easiest way to do this is:
t = Foo.start_time.in_time_zone("America/New_York")
t -= t.utc_offset
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.
Actually, I think you need to subtract the offset after you convert it, as in:
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
Depends on where you are going to use this Time.
When your time is an attribute
If time is used as an attribute, you can use the same date_time_attribute gem:
class Task
include DateTimeAttribute
date_time_attribute :due_at
end
task = Task.new
task.due_at_time_zone = 'Moscow'
task.due_at # => Mon, 03 Feb 2013 22:00:00 MSK +04:00
task.due_at_time_zone = 'London'
task.due_at # => Mon, 03 Feb 2013 22:00:00 GMT +00:00
When you set a separate variable
Use the same date_time_attribute gem:
my_date_time = DateTimeAttribute::Container.new(Time.zone.now)
my_date_time.date_time # => 2001-02-03 22:00:00 KRAT +0700
my_date_time.time_zone = 'Moscow'
my_date_time.date_time # => 2001-02-03 22:00:00 MSK +0400
Here's another version that worked better for me than the current answers:
now = Time.now
# => 2020-04-15 12:07:10 +0200
now.strftime("%F %T.%N").in_time_zone("Europe/London")
# => Wed, 15 Apr 2020 12:07:10 BST +01:00
It carries over nanoseconds using "%N". If you desire another precision, see this strftime reference.
The question's about Rails but it seems, like me, not everyone here is on the ActiveSupport train, so yet another option:
irb(main):001:0> require "time"
=> true
irb(main):003:0> require "tzinfo"
=> true
irb(main):004:0> t = Time.parse("2000-01-01 14:20:00 UTC")
=> 2000-01-01 14:20:00 UTC
irb(main):005:0> tz = TZInfo::Timezone.get("America/New_York")
=> #<TZInfo::DataTimezone: America/New_York>
irb(main):008:0> utc = tz.local_to_utc(t)
=> 2000-01-01 19:20:00 UTC
irb(main):009:0> tz.utc_to_local(utc)
=> 2000-01-01 14:20:00 -0500
irb(main):010:0>
local_to_utc not doing the opposite of utc_to_local might look like a bug but it is at least documented: https://github.com/tzinfo/tzinfo says:
The offset of the time is ignored - it is treated as if it were a local time for the time zone
I managed to do this by calling change with the desired time zone:
>> t = Time.current.in_time_zone('America/New_York')
=> Mon, 08 Aug 2022 12:04:36.934007000 EDT -04:00
>> t.change(zone: 'Etc/UTC')
=> Mon, 08 Aug 2022 12:04:36.934007000 UTC +00:00
https://api.rubyonrails.org/classes/ActiveSupport/TimeWithZone.html#method-i-change
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
Quick little function I came up with to solve the job. If someone has a more efficient way of doing this please post it!
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:
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
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.
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 Ruby / Rails - Change the timezone of a Time, without changing the value.
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:
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 + 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 > 0
dst_ignored_time_with_corrected_offset -= 1.hour
end
dst_ignored_time_with_corrected_offset
end
Examples which can be tried on rails console or a ruby script after wrapping the above methods in a class or module:
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
Hope this helps.
This worked well for me
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)
This changes the timezone to 'EST' without changing the time:
time = DateTime.current
Time.find_zone("EST").local(
time.year,
time.month,
time.day,
time.hour,
time.min,
time.sec,
)
I have this string:
"2011-12-05 17:00:00"
where this is local time
irb(main):034:0> Time.zone
=> (GMT-08:00) Pacific Time (US & Canada)
Now how to I get a Time object with this in UTC?
These don't work:
Time.local("2011-12-05 17:00:00") => 2011-01-01 00:00:00 +0000
Time.local("2011-12-05 17:00:00").utc => 2011-01-01 00:00:00 UTC
UPDATE:
On my local machine, this works:
Time.parse("2011-12-05 17:00:00").utc
=> 2011-12-06 01:00:00 UTC
but on heroku console it doesn't:
Time.parse("2011-12-05 17:00:00").utc
=> 2011-12-05 17:00:00 UTC
It seems that you should use Time.parse instead of Time.local:
require "time"
Time.parse("2011-12-05 17:00:00").utc
Try this in rails application:
Time.zone = "Pacific Time" # => "Pacific Time"
Time.zone.parse("2011-12-05 17:00:00") # => Mon, 05 Dec 2011 17:00:00 UTC +00:00
Details here
I realized my issue was a little more complicated. I wanted to store the times in the database with no time zone, and no time zone conversions. So I left the server and rails app time zone at UTC.
But when I pulled the times out, I would sometimes need to compare them with the current time in the time-zone that the user was in. So I needed to get Time.zone.now for the user, but again, I have Time.zone set to UTC so no automatic conversions happened.
My solution was to pull out the stored user time zone and apply it to Time.now to get the users local time like this:
class Business < ActiveRecord::Base
def tz
TZInfo::Timezone.get(ActiveSupport::TimeZone::MAPPING[self.time_zone])
end
def now
tz.utc_to_local(Time.zone.now)
end
end
So that I could do something like:
#client.appointments.confirmed_in_future(current_business.now)
-
def confirmed_in_future(date_start = Time.zone.now)
confirmed.where("time >= ?", date_start)
end