Say I want the difference between tomorrow and now (in hours).
What I've tried:
t = (DateTime.tomorrow - DateTime.now)
(t / 3600).to_i
=> 0
Why does it give 0?
What am I doing wrong?
This is because DateTime.tomorrow does not have any time value. Here:
DateTime.tomorrow
# => Wed, 22 Apr 2015
If you go through official document for DateTime you can see there is no method tomorrow. Its basically Date#tomorrow.
You can use .to_time to get default localtime 00:00:00
DateTime.tomorrow.to_time
# => 2015-04-22 00:00:00 +0530
(DateTime.tomorrow.to_time - DateTime.now) / 1.hours
# => 9.008116581638655
To get exact hour difference between dates:
(DateTime.tomorrow.to_time - Date.today.to_time) / 1.hours
# => 24.0
Try this
t = (DateTime.tomorrow.to_time - Date.today.to_time)
t = (t / 3600).to_i
It returns rational number. You can take days number if you'll use round method:
>> (DateTime.tomorrow - DateTime.now).round
1
Or if you want to take value in hours from now, use Time class:
>> (Date.tomorrow.to_time - Time.now) / 1.hour
11.119436663611111
if you have two dates like
start_time = Time.new(2015,1, 22, 35, 0)
end_time = Time.new(2015,2, 22, 55, 0)
Try Time Difference gem for Ruby at https://rubygems.org/gems/time_difference
def timediff(start, end)
TimeDifference.between(start, end).in_hours
end
and call it like:
timediff(start_time, end_time)
It will work.
Cheers!
There's DateTime#seconds_until_end_of_day:
seconds = DateTime.now.seconds_until_end_of_day
#=> 41133
seconds / 3600
#=> 11
distance_of_time_in_words(seconds)
=> "about 11 hours"
I have these dates and times:
schedule.day_start # => 2014-09-27 15:30:00 UTC
date_now = Time.now # => 2014-09-27 15:11:14 +0200
date_now + 60.minutes # => 2014-09-27 16:11:14 +0200
I am trying to detect all schedules that start 60 minutes or less before day_start. With the following code, I get as a response "NO" instead of "YES".
if schedule.day_start < (Time.now + 60.minutes)
"YES"
else
"NO"
end
Why is 2014-09-27 15:30:00 UTC bigger than 2014-09-27 16:11:14 +0200?
Work them dates as UTC, so you will avoid time zone problems
if schedule.day_start.utc < (Time.now + 60.minutes).utc
...
Because
2014-09-27 16:11:14 +0200
is simultaneous to
2014-09-27 14:11:14 UTC
which comes before
2014-09-27 15:30:00 UTC
With Time objects, "follows" translates to "greater".
Anywhere, if time A comes after time B, then A is considered to be greater than B. The same is in your case.
schedule.day_start # => 2014-09-27 15:30:00 UTC
date_now + 60.minutes # => 2014-09-27 16:11:14 +0200 which is 2014-09-27 14:11:14 UTC.
Here, you can clearly see that, Time.now + 60.minutes is a timestamp before schedule.day_start. Thus, schedule.day_start is greater than Time.now + 60.minutes, that's why your "if" case doesn't hold true and hence NO is printed.
Rememeber your result is false because the GMT, to resolve this and compare the only datetime without GMT using UTC, try this:
minutes = 60.minutes
t1 = Time.at(schedule.day_start.utc).to_datetime
t2 = Time.at((Time.now + minutes).utc).to_datetime
if t1 < t2
"YES"
else
"NO"
end
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 want easiest or simplest method which returns me boolean value (true/false) depending on the given time is after 3 pm or not irrespective of date.
for ex:-
def after_three_pm(time)
//some code here
end
time= Time.now # Tue Jul 26 11:17:27 +0530 2011 THEN
after_three_pm(time) # should return false
time= Time.now # Tue Jul 26 15:17:27 +0530 2011 THEN
after_three_pm(time) # should return true
def after_three_pm(time)
time.hour >= 15
end
is all you need.
you simply need to use the "time" function:
Time.now.hour
=> 11
Now you can just evaluate this against the hour you want.
I was wondering if there's a way in Rails to calculate time stamp like - half a minute ago, 2 minute ago, 1 day ago etc. Something like twitter real time date stamp.
I want to know if Ruby/Rails has a built-in function for such date-time conversion?
You can use:
10.minutes.ago
2.days.since
Or in your views you have the helpers:
distance_of_time_in_words(from_time, to_time)
time_ago_in_words(from_time)
Check the API for details and more options.
You can use available methods to get the time in past or future using ago, since alias for from_now and many available methods
Time.current
#=> Tue, 20 Sep 2016 15:03:30 UTC +00:00
2.minutes.ago
#=> Tue, 20 Sep 2016 15:01:30 UTC +00:00
2.minutes.since
#=> Tue, 20 Sep 2016 15:05:30 UTC +00:00
1.month.ago
#=> Sat, 20 Aug 2016 15:03:30 UTC +00:00
1.year.since
#=> Wed, 20 Sep 2017 15:03:30 UTC +00:00
Check all the available methods in Time class
distance_of_time_in_words:
from_time = Time.now
distance_of_time_in_words(from_time, from_time + 50.minutes) # => about 1 hour
distance_of_time_in_words(from_time, 50.minutes.from_now) # => about 1 hour
distance_of_time_in_words(from_time, from_time + 15.seconds) # => less than a minute
distance_of_time_in_words(from_time, from_time + 15.seconds, include_seconds: true) # => less than 20 seconds
time_ago_in_words:
time_ago_in_words(3.minutes.from_now) # => 3 minutes
time_ago_in_words(3.minutes.ago) # => 3 minutes
time_ago_in_words(Time.now - 15.hours) # => about 15 hours