I'm getting a datetime field from an API that does not explicitly set its timezone. When I place this into a database it's assuming the datetime must be in GMT, but the timezone is actually in Chicago time. (I say Chicago time, because I'm still unsure if this API factors in DST.) What is the best way for me to convert this time to GMT before adding it to the database?
Here is an XML sample of one of the nodes I'm referring to:
<FromDateTime>2011-03-17 08:00:00</FromDateTime>
In Ruby, I'm using this to add this record to the database.
:starttime => DateTime.parse(row.at_xpath("FromDateTime/text()").to_s),
I think what I need to do is add the difference in hours between CST and GMT to this last Ruby call, right? How would I do that?
Thanks!
Could you use Time instead? DateTime is not Daylight Savings Time aware. Time automatically sets to your local GMT offset for the given date/time and set DST if needed.
irb(main):014:0> require 'time'
irb(main):015:0> Time.parse('2011-03-17 08:00:00')
=> Thu Mar 17 08:00:00 -0400 2011
irb(main):022:0> Time.parse('2011-03-17 08:00:00').dst?
=> true
Here is the case for standard time (I am in EST)
irb(main):025:0> Time.parse('2011-01-17 08:00:00')
=> Mon Jan 17 08:00:00 -0500 2011
irb(main):023:0> Time.parse('2011-01-17 08:00:00').dst?
=> false
If you are using ActiveSupport http://api.rubyonrails.org/classes/DateTime.html you can set to arbitrary time zone:
irb(main):039:0> Time.zone = 'America/Chicago'
=> "America/Chicago"
irb(main):040:0> Time.parse('2011-03-17 08:00:00')
=> Thu Mar 17 08:00:00 -0400 2011
Related
I configured my time zone to indian time zone in my Rails app by adding this line config.time_zone = 'Mumbai' to my application.rb file.
I am having a date time field t.datetime :check_in in my table. To this check_in column I am saving the server time like this Person.check_in = DateTime.now. When I save like this, the time is saving properly, with the time zone configured in the app. after that for some reason when I update like this Person.check_in = "24/08/2015 11:50 AM".to_datetime it is not saving the time with the time zone I configured. Below is my rails console output:
prashant#prashant-pc:~/client_proj/template$ rails c
Loading development environment (Rails 4.1.5)
2.2.2 :001 > check_in = DateTime.now
=> Mon, 24 Aug 2015 11:41:16 +0530
2.2.2 :003 > "24/08/2015 11:42 PM".to_datetime
=> Mon, 24 Aug 2015 23:42:00 +0000
2.2.2 :004 >
This is unfortunately the designed behavior of to_datetime function.
This other question is what you are after. They provide the following alternatives:
Time.zone.parse('24/08/2015 11:50 AM').to_datetime
or even:
"24/08/2015 11:50 AM".to_datetime.in_time_zone("Mumbai")
Use in_time_zone from ActiveSupport::TimeWithZone
"2015-08-14 14:38".to_datetime.in_time_zone('Mumbai')
=> Fri, 14 Aug 2015 20:08:00 IST +05:30
"2015-08-14 14:38".to_datetime.in_time_zone('Eastern Time (US & Canada)')
=> Fri, 14 Aug 2015 10:38:00 EDT -04:00
Time.now.in_time_zone("Mumbai")
=> Sat, 22 Aug 2015 12:38:32 IST +05:30
Time.now.in_time_zone("Pacific Time (US & Canada)")
=> Sat, 22 Aug 2015 00:08:21 PDT -07:00
Actually, there are several ways to do the same thing e.g. using Time.zone.local, Time.zone.parse etc. See the above link for more examples.
To, answer your exact question, to pass the time_zone configured in your application.rb file, you have to use this:
check_in = DateTime.now
check_in.in_time_zone(Rails.application.config.time_zone).to_datetime
Use local time gem. It will display the time in local time zone no matter where you are.
It is very good solution as you will don't have to call in time zone method every time you show a date in your views. The Gem has very good documentation as well. Visit https://github.com/basecamp/local_time
I have an app where different users are in different parts of the globe (I know their timezone), and they can enter dates and times, and I need to store everything in UTC on the DB.
Normally to instance my Time variable, I'm doing:
DateTime.new(date.year, date.month, date.day, hours, minutes, 0)
This is already in UTC, but without converting.
If I add a 7th parameter to that string with the time_zone (ie. "Melbourne"), then it will interpret it as a a date in Australia, and the resulting DateTime, when converted to UTC, is 10-ish hours behind, and that works.
However, that's not taking into account Daylight Saving.
What I need is to do exactly that (instance a DateTime from the components of a date/time), such that (in the case of Australia, for example), using the same hours/minutes for April 9th will give me a different offset when converted to UTC than if I used April 5th.
Any ideas?
Thanks!
Daniel
Have a look at tzinfo
irb(main):002:0> require 'tzinfo'
=> true
irb(main):003:0> tz = TZInfo::Timezone.get("Australia/Melbourne")
=> #<TZInfo::DataTimezone: Australia/Melbourne>
irb(main):004:0> tz.utc_to_local(Time.parse("2013-04-05 00:00:00"))
=> Fri Apr 05 11:00:00 UTC 2013
irb(main):005:0> tz.utc_to_local(Time.parse("2013-04-09 00:00:00"))
=> Tue Apr 09 10:00:00 UTC 2013
irb(main):015:0> tz.local_to_utc(Time.parse("2013-04-09 00:00:00"))
=> Mon Apr 08 14:00:00 UTC 2013
irb(main):016:0> tz.local_to_utc(Time.parse("2013-04-05 00:00:00"))
=> Thu Apr 04 13:00:00 UTC 2013
Just adding to the million questions about time zone and DST issues out there.
I have a form with separate date and time fields that I combine to create a DateTime like so
start_time = DateTime.parse("#{parse_date(form_date)} #{form_start_time} #{Time.zone}")
If I fill out my form with 21 Aug 2012 and 15:00, then these are the values that I see when I reload my form. If I then look at my start_time attribute in my model it is correctly set to Tue, 21 Aug 2012 15:00:00 EST +10:00.
The problem I am having occurs if I use a date later this year once daylight savings kicks in (I am in Australia). If I use 21 Dec 2012 and 15:00 then check start_time I see Fri, 21 Dec 2012 16:00:00 EST +11:00.
My interpretation of the problem is that the date is being saved in my current time zone (+10:00) as this is what I have told DateTime.parse to do. However when the value is returned, Rails is looking at the date and saying 'hey, it's daylight savings time in December' and returning the time in the +11:00 time zone.
What I want to do is tell DateTime.parse to save the time in the +11:00 time zone if DST is in effect. Clearly passing Time.zone into my string doesn't achieve this. Is there a simple way of doing this? I can see ways of doing it using Time#dst? but I suspect that this is going to create some really ugly convoluted code. I thought there might be a built in way that I'm missing.
(Answer for Rails 4.2.4, didn't check for older or newer versions)
Instead of using fixed shift +01:00, +02:00, etc, I recommend to use the in_time_zone String method with time zone name as argument :
Summer time :
ruby :001 > "2016-07-02 00:00:00".in_time_zone('Paris')
=> Sat, 02 Jul 2016 00:00:00 CEST +02:00
Winter time :
ruby :002 > "2016-11-02 00:00:00".in_time_zone('Paris')
=> Wed, 02 Nov 2016 00:00:00 CET +01:00
String#in_time_zone is the equivalent of :
ruby :003 > Time.find_zone!("Paris").parse("2016-07-02 00:00:00")
=> Sat, 02 Jul 2016 00:00:00 CEST +02:00
ruby :004 > Time.find_zone!("Paris").parse("2016-11-02 00:00:00")
=> Wed, 02 Nov 2016 00:00:00 CET +01:00
You can get the time zone names by :
$ rake time:zones:all
Or in rails console :
ruby :001 > ActiveSupport::TimeZone.all.map(&:name)
Or build collection for select tag :
ActiveSupport::TimeZone.all.map do |timezone|
formatted_offset = Time.now.in_time_zone(timezone.name).formatted_offset
[ "(GMT#{formatted_offset}) #{timezone.name}", timezone.name ]
end
And store the time zone name instead of the shift.
Note : don't confuse String#in_time_zone method and the Time#in_time_zone method.
consider the time zone for my system is 'Paris'.
ruby :001 > Time.parse("2016-07-02 00:00:00")
=> 2016-07-02 00:00:00 +0200
ruby :002 > Time.parse("2016-07-02 00:00:00").in_time_zone("Nuku'alofa")
=> Sat, 02 Jul 2016 11:00:00 TOT +13:00
Here's my solution so far. I'm hoping someone has a better one.
start_time = DateTime.parse "#{date} #{(form_start_time || start_time)} #{Time.zone}"
start_time = start_time - 1.hour if start_time.dst? && !Time.now.dst?
start_time = start_time + 1.hour if Time.now.dst? && start_time.dst?
It seems to work but I haven't rigorously tested it. I suspect it could be prettied up and shortened but I think this is readable and understandable. Any improvements?
I ran into this exact issue. My app allows users to see upcoming events. In the US we fall of DST on November 2nd and all events on and after that date were showing times an hour early.
We require the opportunity to have the timezone selected and stored to its own field. Before I was using the following to store my datetime:
timezone_offset = Time.now.in_time_zone(params[:opportunity][:time_zone]).strftime("%z") #-0700
DateTime.parse("#{params[:opportunity][:start_datetime]} #{timezone_offset}")
To fix the issue I have changed to:
start_datetime = Time.zone.parse(params[:opportunity][:start_datetime])
To display the correct times we use:
#opportunity.start_datetime.in_time_zone(#opportunity.time_zone)
I wouuld try and use
Australian Eastern Standard Time (AEST) (UTC +10).
Australian Central Standard Time (ACST) (UTC +9 ½).
Australian Western Standard Time (AWST) (UTC +8).
which adjust for Daylight Savings.
With Rails, we can use ActiveSupport::TimeZone for this:
tz = ActiveSupport::TimeZone.new 'Pacific Time (US & Canada)'
tz.parse(date_str_without_zone).to_datetime
I use TZip to get TimeZone strings (e.g. "Pacific Time (US & Canada)") from zip codes.
In case you have a custom date/time format, different than the supported by String#in_time_zone, you could also use (since rails 5) strptime like:
Time.find_zone!('Auckland').strptime('2021-02-02 08.00.00', '%Y-%m-%d %H.%M.%S')
I added this line of code
self.auth_history.push [start_date, self.coupon_code]
And got this error message
Date is not currently supported; use a UTC Time instance instead.
I also tried start_date.utc, but it didn't work either.
Please help. Thanks.
I got this answer from Seattle Brigade group -
===
I didn't see start_date defined in your code as a key in MongoMapper, so
I'll assume you're creating your own date object, either directly via Ruby,
or wrapped by Rails. As far as I know, and someone please correct me, Mongo
stores dates as UTC time in milliseconds since epoch. So when you define a
key with a :date mapping in MongoMapper, you're wrapping a Time object in
Ruby.
Therefore, if you want to store a date inside of Mongo, and it wasn't
created by MongoMapper, make sure you create a Time object in UTC.
MongoMapper comes with a Date mixin method called to_mongo that you can use.
>> Time.now.utc
=> Fri Jan 28 03:47:50 UTC 2011
>> require 'date'
=> true
>> date = Date.today
=> #<Date: 4911179/2,0,2299161>
>> Time.utc(date.year, date.month, date.day)
=> Thu Jan 27 00:00:00 UTC 2011
>> require 'rubygems'
=> true
>> require 'mongo_mapper'
=> true
>> Date.to_mongo(date)
=> Thu Jan 27 00:00:00 UTC 2011
But watch out for the time change.
>> Date.to_mongo(Time.now)
=> Thu Jan 27 00:00:00 UTC 2011
>> Date.to_mongo(Time.now.utc)
=> Fri Jan 28 00:00:00 UTC 2011
Good luck.
===
And by using
Date.to_mongo(start_date)
it works for me.
First, I think the question title is bad in description. Actually, the difference between different timezone is on Time not on Date. So, it's really not proper to say I want to convert a date to UTC format.
Here is another way in Ruby to convert DateTime to its UTC format:
DateTime.now.new_offset(0)
Here's another option:
Time.at(Date.today.to_datetime.to_i).utc
Here I am using Date.today as an arbitrary example date. Replace with whatever date you want to convert. Once the date is converted to a Time instance, it can be serialized to BSON without any problem, as Time is a supported primitive type, that is to say, it can be saved using MongoMapper to the database.
As per EfratBlaier's comment I have updated the answer.
Date.today.to_time.utc
I have a rails time-based query which has some odd timezone sensitive behaviour, even though as far as I know I'm using UTC. In a nutshell, these queries give different answers:
>> Model.find(:all,:conditions=>['created_at<=?',(Time.now-1.hours).gmtime]).length
=> 279
>> Model.find(:all,:conditions=>['created_at<=?',(Time.now-1.hours)]).length
=> 280
Where the DB actually does contain one model created in the last hour, and the total number of models is 280. So only the first query is correct.
However, in environment.rb I have:
config.time_zone = 'UTC'
The system time zone (as reported by 'date') is BST (which is GMT+1) - so somehow this winds up getting treated as UTC and breaking queries.
This is causing me all sorts of problems as I need to parameterise the query passing in different times to an action (which are then converted using Time.parse()), and even though I send in UTC times, this 'off by one hour' DST issue crops a lot. Even using '.gmtime()' doesn't always seem to fix it.
Obviously the difference is caused somehow by an implicit conversion somewhere resulting in BST being incorrectly treated as UTC, but why? Doesn't rails store the timestamps in UTC? Isn't the Time class timezone aware? I am using Rails 2.2.2
So what is going on here - and what is the safe way to program around it?
edit, some additional info to show what the DB and Time class are doing:
>> Model.find(:last).created_at
=> Tue, 11 Aug 2009 20:31:07 UTC +00:00
>> Time.now
=> Tue Aug 11 22:00:18 +0100 2009
>> Time.now.gmtime
=> Tue Aug 11 21:00:22 UTC 2009
The Time class isn't directly aware of your configured timezone. Rails 2.1 added a bunch of timezone support, but Time will still act upon your local timezone. This is why Time.now returns a BST time.
What you likely want is to interact with Time.zone. You can call methods on this like you would the Time class itself but it will return it in the specified time zone.
Time.zone.now # => Tue, 11 Aug 2009 21:31:45 UTC +00:00
Time.zone.parse("2:30 PM Aug 23, 2009") # => Sun, 23 Aug 2009 14:30:00 UTC +00:00
Another thing you have to be careful with is if you ever do queries on the database where you are comparing times, but sure to use the UTC time (even if you have a different time zone specified) because Rails always stores UTC in the database.
Item.all(:conditions => ["published_at <= ?", Time.now.utc])
Also, instead of Time.now-1.hour do 1.hour.ago. It is easier to read and Rails will automatically use the configured timezone.
The TimeZone you need to set is UK, this will automatically handle BST
Time.zone = 'UK'
Time.zone.now
=> Sun, 17 Oct 2010 02:09:54 BST +01:00
start_date_format = DateTime.strptime(#start_date, date_format)
start_date_format_with_hour =
DateTime.strptime((start_date_format.to_i + timezone_offset*60*60).to_s,'%s').strftime(date_format)
end_date_format = DateTime.strptime(#end_date, date_format)
end_date_format_with_hour = DateTime.strptime((end_date_format.to_i + timezone_offset*60*60).to_s,'%s').strftime(date_format)
#filters_date = "invoices.created_at >= ? AND invoices.created_at < ?", start_date_format_with_hour, end_date_format_with_hour