Timezone & DST help

rubyonrails-talk
1

TL;DR - gist:5035116 · GitHub

I have a datetime picker in my app (Adding a Timepicker to jQuery UI Datepicker). When someone clicks in a text_field, the picker pops up and displays the calendar with the time, and timezone.

I have the timezones for that select box populated like this

var timezones = function() {   zones = [   <% ActiveSupport::TimeZone.all.sort_by(&:name).each_with_index do

timezone, index| %>

    { value: '<%= timezone.formatted_offset(false) %>', label: "<%= timezone.name %>" },   <% end %>   ]

  return zones; };

The issue I'm running into is that when someone selects "Pacific Time (US & Canada)" the value of that option is "-0800". If the date they selected is after March 10th (2013), then the "Pacific Time (US & Canada)" time zone is actually "-0700". So what happens is they save the record as 2013-03-15 08:00 pm -0800, then it gets stored in the DB as Fri, 15 Mar 2013 21:00:00 PDT -07:00.

Now, if they save the date as before March 10th (2013), then it saves the correct time.

So, is there some method in rails where I can pass a date, and it will return the proper offset for any time zone with DST into consideration?

Thanks, ~Jeremy

2

Ok, I think I've come up with 2 solutions.

1. Go with Javascript http://www.datejs.com/    Date.parse("2013-03-09").getUTCOffset() // "-0800"    Date.parse("2013-03-10").getUTCOffset() // "-0700"

2. Parse it in ruby    Time.parse("2013-03-09 20:00:00").localtime.strftime("%z") # "-0800"    Time.parse("2013-03-10 20:00:00").localtime.strftime("%z") # "-0700"

In case anyone else comes across this. I'm just praying this works internationally O_o

3

Jeremy Woertink wrote in post #1099164:

The issue I'm running into is that when someone selects "Pacific Time (US & Canada)" the value of that option is "-0800". If the date they selected is after March 10th (2013), then the "Pacific Time (US & Canada)" time zone is actually "-0700". So what happens is they save the record as 2013-03-15 08:00 pm -0800, then it gets stored in the DB as Fri, 15 Mar 2013 21:00:00 PDT -07:00.

I think that's problem #1. In order to provide global timezone support you should store all date/time values in UTC in the database and translate the date/time into the local timezone of the server.

It is also often necessary to display dates and time in the local time zone of the user, which means you'll need to ask the user their time zone and store that with the user.

Example: 2013-03-15 08:00 pm -0800 => 2013-03-15 16:00:00 UTC

Now timezone is no longer an issue... UTC is UTC everywhere, that's the point. If configured properly Rails should take care of this for your automatically.

If you do need to display the time in the local time zone of the user then you can.

utc_time.in_time_zone("Pacific Time (US & Canada)")

Note: in_time_zone is a Rails convenience.