I'm having a frustrating issue that I can't seem to narrow down. I have searched many similar articles but they are not close enough to my issue to resolve. I am trying to pull a time from the database and display it in more than one time zone. My Rails app is using UTC as default. Here is what I'm doing:
On the create action I take the string of time which will be saved in the time column in my DB:
params[:schedule][:start] = "09:00"
Time.zone = "Central Time (US & Canada)"
#schedule.start = Time.zone.parse(params[:schedule][:start])
The above formats the time as it is supposed to:
2016-04-12 09:00:00 -0500
This is saved in the DB as:
2000-01-01 14:00:00
This has no time offset which is fine since I know it's in UTC. The problem happens when I go to display the time:
#schedule.start.in_time_zone("Central Time (US & Canada)")
This returns:
Sat, 01 Jan 2000 08:00:00 CST -06:00
Now, since this is a time column, I don't care about the date. I plan on formatting the value to only show the time. However, it is showing CST when it is currently CDT.
I can't figure out why this is happening. As I said I am not setting the Time Zone anywhere in my application.rb or anywhere else and I only set the Time zone on the create action which should be fine when moving to a new action.
Any help on clarifying this would be awesome!
This seems to be because when the time is stored it is stored with the date in the year 2000-01-01 which seems to be why it is using CST. How can I ignore the date when converting it to a particular timezone or will I need to change the column type to DateTime to get this to work properly?
It is showing CST simply because the time is read from the database including the stored date, i.e. it's read as 09:00 of Jan 1st 2000.
I guess you'd have to parse the time upon reading the attribute back. You can use a helper method in your model, for example:
# schedule model
def start_in_zone(zone)
self.start.strftime("%H:%M").in_time_zone(zone)
end
This will take only the hours and minutes part of the stored time and parse it in the given time zone with the date set to today. See this example:
"Sat, 01 Jan 2000 08:00:00".to_time.
strftime("%H:%M").
in_time_zone("Central Time (US & Canada)")
# => Tue, 12 Apr 2016 08:00:00 CDT -05:00
The fact that it matters whether it's CST or CDT means you do, on some level, care about the date. While I'm not familiar with the exact rules of Daylight Savings in that region, I do know that Jan 1 is the middle of winter and will definitely not be on Daylight Savings time.
Add the relevant date into your #schedule before putting it into a time zone, and it should fix the problem.
Related
I have records with a created column whose datetime is stored in UTC.
For instance, this is the datetime stored in one record: 2014-02-01 00:33:25
But if I retrieve that record and confer it to CST, it'd look like this:
Article.find(1).created.in_time_zone('Central Time (US & Canada)') => Fri, 31 Jan 2014 18:33:25 CST -06:00
Which is a different day/month as far as that timezone goes.
The problem I'm having is finding records based on a date. So say I wanted to pull all records for January 31, 2014 (CST). I want to include my example record.
How do I do that in a Rails app? I'm running Rails 4.0.1 and Ruby 2.0.0 with Postgres 9.3.1.0.
Use AT TIME ZONE to change timezone
Article.where("date(created AT TIME ZONE 'UTC' AT TIME ZONE 'CST') = '01/31/2014'")
Got some help outside of SO and got what I was looking for.
Say I wanted to find all records in a date range, this is what it'd be:
Article.where(created: Date.parse("January 1, 2014").in_time_zone('Central Time (US & Canada)').beginning_of_day.utc..Date.parse("January 31, 2014").in_time_zone('Central Time (US & Canada)').end_of_day.utc)
I am working on a rail4 app. Where I want to store dates in all mysql tables in UTC. However I store user's timezone in a specific table, called users. When user logs in, I get user's timezone form user table and save in session.
I am able to save date in all tables in UTC as default value of config.time_zone is UTC for activerecords and activemodels. But while displaying I want to show dates in user's timezone. As well as, when any user inputs a date/time in any html form, then I want to save it in the equivalent UTC format.
What is the best way to achieve this?
Rails, activerecord and MySQL will save all the timestamp fields in UTC. Without you having to do anything.
In your application.rb file where the configuration of the Application is done, you define the default time zone if you want the display of timestamps to take place on time zone different from UTC.
Hence
config.time_zone = 'Central Time (US & Canada)'
will display the timestamp fields (without you having to do anything special in other piece of code) using the Central Time.
When you want each of your users to have timestamps displayed in different time zone you can store the time zone in a column along side the user data. The column can be called time_zone and can contain the string of the user preferred time zone.
But, you have to tell the timestamp object to display itself to the specific timezone. This is done with the help of the method in_time_zone(timezone) that DateTime object responds to.
Example (when the default time zone is UTC):
1.9.3-p194 :004 > d = DateTime.new(2012, 9, 1, 6, 30, 0)
=> Sat, 01 Sep 2012 06:30:00 +0000
1.9.3-p194 :005 > d.in_time_zone("Central Time (US & Canada)")
=> Sat, 01 Sep 2012 01:30:00 CDT -05:00
Or you can change the time zone globally for the request at hand on a before or around filter. There is a documentation on internet if you do a google on that.
Read also this one: http://api.rubyonrails.org/classes/ActiveSupport/TimeWithZone.html
for various alternatives to approach the problem.
You could store the time in UTC, and store the timezone separately. Timezones are commonly stored as a UTC-offset in seconds (seconds are the SI unit of time).
Then you can display it like so:
utime = Time.now.utc.to_i # this value can be any format that Time.at can understand. In this example I'll use a unix timestamp in UTC. Chances are any time format you store in your DB will work.
=> 1375944780
time = Time.at(utime) # parses the time value (by default, the local timezone is set, e.g. UTC+08:00)
=> 2013-08-08 14:53:00 +0800
time_in_brisbane = time.in_time_zone(ActiveSupport::TimeZone[36000]) # sets the timezone, in this case to UTC+10:00 (see http://stackoverflow.com/a/942865/72176)
=> Thu, 08 Aug 2013 16:53:00 EST +10:00
time_brisbane.strftime("%d %b %Y, %l:%M %p %z") # format with strftime however you like!
=> "08 Aug 2013, 4:53 PM +1000"
Running this code...
Time.use_zone('Pacific Time (US & Canada)') do
p Time.zone.now
end
I get the following: => Sun, 14 Apr 2013 20:30:53 PDT -07:00
Yet when I do Rails Time Zone Select.... it says -8:00 quite clearly. Why is it -7 in one area and -8 in another?
Other times, time zones like Hawaii which are -10:00 don't get offset by an hour.
I assume this has something to do with DST, but I'm more curious whether it means it's working properly or improperly and there is something else I need to do.
Ultimately I'm using this in a datepicker, and I find it very odd that when I use Time.zone.parse (along with my time zone around filter), its offsetting everything by 1 hour.
THanks
My app is working in "Moscow" (+04:00) timezone. But sometimes I need to create time object by only local time (for example "01 may 2012 13:45") and name of ActiveSupport::TimeZone object (for example "Berlin": +02:00 in Summer Time and +01:00 otherwise).
For example if I get "01 may 2012 13:45" and "Berlin" as input I want to yield "2012-05-01 13:45:00 +0200" or "2012-05-01 11:45:00 +0000". I create following function:
def from_local_datetime(local_datetime, time_zone)
offset = Time.now.in_time_zone(time_zone).formatted_offset
datetime = case local_datetime
when String
DateTime.parse(local_datetime)
else
DateTime.new(local_datetime)
end.change(:offset => offset)
return datetime
end
And at the first look it works as I expected. But is it a best practice for this kind of task? May be in some situation It works with errors. I'm not definitely sure.
I would be greatful to any comments.
UPD: I think bug may occur about time when DST changing the time. For example 26 march 2011 was GMT+1 in Berlin time zone and Time.now.in_time_zone("Berlin").formatted_offset returns "GMT+1", but it would be GMT+2 in 27 march 2011. So if I call from_local_datetime("28 march 2011", "Berlin") before 27 march it returns 28 march 2011 00:00:00 +0100, but If I call it after changing the time my function returns 28 march 2011 00:00:00 +0200 :(
Your conversion method is the right approach.
With web sites, you should make sure times are stored as UTC in the database. If you can get the UTC value out of the database, instead of the local time (or maybe you can set your web server's time zone to UTC) it won't have to convert the time from UTC to local time, when you are going to then convert it to the user's timezone anyway.
And, of course, you will have to store the user's time zone preference.
TZInfo::Timezone.get('Europe/London')
Find the time zone
http://api.rubyonrails.org/classes/ActiveSupport/TimeZone.html
I am trying to find events on certain days with this code:
Event.where('starttime BETWEEN ? AND ?', DateTime.now.beginning_of_day, DateTime.now.end_of_day)
In rails console if I run DateTime.now.beginning_of_day I get exactly what I expect:
Mon, 09 Apr 2012 00:00:00 -0700
I can see where the problem is occurring but looking at the SQL in rails console. Somehow when the date makes it into the SQL query it gets automatically formatted to the wrong date and time.
SELECT "events".* FROM "events" WHERE (starttime BETWEEN '2012-04-09 07:00:00' AND '2012-04-10 06:59:59')
This is giving me results that vary from today until tomorrow, as the sql above says. I can see that when the DateTime.now.beginning_of_day also DateTime.now.end_of_day are being formatted incorrectly once they make it into the sql query. Do I need to be formatting this in a certain way? Any idea why it would go to 7:00 of today and 7:00 of tomorrow?
I don't know if it makes a difference but I'm using PostgreSQL.
Thanks!
See: http://railscasts.com/episodes/106-time-zones-in-rails-2-1
I think the times you're quoting above are actually the same time, just one is UTC time (you're on pacific time right?). To fix this you could try setting:
config.time_zone = "Pacific Time (US & Canada)"
in your environment.rb
You could also try:
DateTime.now.utc.beginning_of_day
DateTime.now.utc.end_of_day
so the you're using UTC as per the DB
You are probably using UTC time in your database. This is a good thing but it leads to all sorts of confusion. The -0700 offset is converted to 07:00:00 since that's when your day starts in UTC time.
You could use the PostgreSQL AT TIME ZONE construct with UTC timestamps:
SELECT e.*
FROM events e
WHERE starttime >= '2012-04-09 00:00' AT TIME ZONE 'UTC'
AND starttime < '2012-04-10 00:00' AT TIME ZONE 'UTC'
I recently explained PostgreSQL timestamp and time zone handling in a related answer.