I got two models Shift and ShiftDetail. I have a Shift model methods that adds ShiftDetails automatically:
def add_shift_details
(0..6).each do |i|
shift_detail = ShiftDetail.new
t1 = Time.now
shift_detail.weekday = i
shift_detail.start_time = t1.beginning_of_day
shift_detail.end_time = t1.end_of_day
self.shift_details << shift_detail
end
end
But when i save the instance the database is populated with
["start_time", "2016-03-02 23:00:00.000000"]
["end_time", "2016-03-03 22:59:59.999999"]
I am using Rails 4.2.5.1 and ruby 2.3.0p0
What am I doing wrong?
UPDATE:
When I test it in 'rails c', it works as expected:
2.3.0 :001 > Time.now.beginning_of_day
=> 2016-03-03 00:00:00 +0100
2.3.0 :002 > Time.now.end_of_day
=> 2016-03-03 23:59:59 +0100
Your database stores DateTime in the UTC timezone while Rails works with the Berlin timezone. Berlin's midnight (GMT+1) is not equal with UTC's (GMT) midnight :)
You have two options:
Have your algorithm work with an UTC timezone
You can use Time.now.utc or DateTime.now.new_offset(0)
Have your database store dates in your specific timezone (Berlin's in this case). I highly advise not to do this.
Check out this post for more information:
https://stackoverflow.com/a/32229086/4304188
I have a column that has a datetime data types.
Whenever I update the column like this.
new_date = "2014-12-13 03:43:30".to_datetime
Model.first.update_column(:my_datetime, new_date) => true
But when I do quest like this.
Model.first.my_datetime => "Sat, 13 Dec 2014 11:43:30 HKT +08:00"
It supposed to output 03:43:30
Please help thanks!
you are looking for strftime:
new_date.strftime("%T")
#=> "03:43:30"
or applying it on activerecord response:
new_date = "2014-12-13 03:43:30".to_datetime
Model.first.update_column(:my_datetime, new_date)
#=> true
Model.first.my_datetime.strftime("%T")
#=> "03:43:30"
Here %T is for Local time (extended)
You need to change the Zone
Use Time.zone.now
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,
)
My application.rb:
config.time_zone = 'Moscow'
config.time_zone = "(GMT+04:00) Moscow"
config.active_record.default_timezone = 'Moscow'
config.active_record.default_timezone = :local
When i run this commands, i get:
1.9.3-p362 :001 > Time.now
=> 2013-02-14 14:18:42 +0400
1.9.3-p362 :002 > Time.zone.now
=> Thu, 14 Feb 2013 10:18:52 UTC +00:00
So in db i see 10:18:52 UTC +00:00.
But what and how to configure, to see such time, as in Time.Now? (when i insert new row to db i must see time, as given by Time.now, what to configure?)
Server's time is Moscow....
also db is mysql
You can use local time like this:
> current_time = Time.now.utc
=> 2013-02-14 15:15:58 UTC
> current_time .localtime
=> 2013-02-14 10:15:58 -05 hours
You can use also:
Time.now.utc.in_time_zone("Moscow")
But for the answer to your question, the solution could be to set it like this:
config.time_zone = 'Moscow' (don't set this - delete this line)
config.active_record.default_timezone = :local
And also you can use your local time something like this:
Time.local_time
I hope some of this approaches might help you
In your application.rb include these lines:
config.time_zone = 'Moscow'
config.active_record.default_timezone = 'Moscow'
Now that you have set the time zone:
Time.now
=> 2013-02-14 11:14:46 +0000
Time.current
=> Thu, 14 Feb 2013 15:14:48 MSK +04:00
user = User.create(name: 'test')
=> #<User id: 6, name: "test", created_at: "2013-02-14 11:15:00", updated_at: "2013-02-14 11:15:00">
user.created_at
=> Thu, 14 Feb 2013 15:15:00 MSK +04:00
As you can see, despite the fact that rails stores the time as UCT +0000 (very clever btw), the rails interface is providing the required offset. If you call any object, such as user.created_at it will offset the database time to return the zone time.
It is very useful, because it allows the configuration of different time zones for different users. The time will be stored without offset, but each user will get its equivalent time zone.
Time.now return +00:00, doesn't matter your time zone.
Time.current is the same as Time.zone.now.
ruby-1.9.2-p0 > SalesData.last
=> #<SalesData id: 196347, created_at: "2011-04-05 18:53:15", updated_at: "2011-04-05 18:53:15">
ruby-1.9.2-p0 > SalesData.last.created_at
=> Tue, 05 Apr 2011 20:53:21 CEST +02:00
application.rb:
config.time_zone = 'Copenhagen'
I don't get it - anyone?
I assume you're asking why the created_at datetimestamps appear to differ. In short, they don't.
Rails always stores datetimes in UTC, converting them to your configured timezone on the fly while loading the record. I don't know exactly when that conversion happens, but I'm betting you're just seeing those two states.