How to convert DateTime.now to UTC in Ruby?

Question

If I have d = DateTime.now , how do I convert 'd' to UTC (with the appropriate date)?

Answer 1

d = DateTime.now.utc hit>

Unfortunately,

This seems to work in Rails, but not in vanilla Ruby (and, of course, this is the question that asks the question)

 d = Time.now.utc 

However, does it work.

Is there a reason you need to use DateTime rather than Time ? Time should include everything you need:

 irb(main):016:0> Time.now => Thu Apr 16 12:40:44 +0100 2009 

Answer 2

 DateTime.now.new_offset(0) 

will work in standard Ruby (i.e. without ActiveSupport).

Answer 3

Unfortunately, the DateTime class does not have the convenience methods available in the Time class for this. You can convert any DateTime object to UTC as follows:

 d = DateTime.now d.new_offset(Rational(0, 24)) 

You can switch from UTC to localtime using:

 d.new_offset(DateTime.now.offset) 

where d is a DateTime object in UTC. If you want these methods to be convenient, you can create them as follows:

 class DateTime def localtime new_offset(DateTime.now.offset) end def utc new_offset(Rational(0, 24)) end end 

You can see this in action in the following irb session:

 d = DateTime.now.new_offset(Rational(-4, 24)) => #<DateTime: 106105391484260677/43200000000,-1/6,2299161> 1.8.7 :185 > d.to_s => "2012-08-03T15:42:48-04:00" 1.8.7 :186 > d.localtime.to_s => "2012-08-03T12:42:48-07:00" 1.8.7 :187 > d.utc.to_s => "2012-08-03T19:42:48+00:00" 

As you can see above, the original DateTime object has an offset of -04: 00 (Eastern Time). I am in Pacific Time with an offset of -07: 00. Calling localtime , as described earlier, correctly converts the DateTime object to local time. Calling utc on an object correctly converts it to a UTC offset.

Answer 4

You can set ENV if you want your Time.now and DateTime.now respond in UTC.

 require 'date' Time.now #=> 2015-11-30 11:37:14 -0800 DateTime.now.to_s #=> "2015-11-30T11:37:25-08:00" ENV['TZ'] = 'UTC' Time.now #=> 2015-11-30 19:37:38 +0000 DateTime.now.to_s #=> "2015-11-30T19:37:36+00:00" 

Answer 5

In irb:

 >>d = DateTime.now => #<DateTime: 11783702280454271/4800000000,5/12,2299161> >> "#{d.hour.to_i - d.zone.to_i}:#{d.min}:#{d.sec}" => "11:16:41" 

converts time to utc. But as indicated, if it's just Time, you can use:

 Time.now.utc 

and get it right away.

Answer 6

The string representation of DateTime can be parsed by the Time class.

 > Time.parse(DateTime.now.to_s).utc => 2015-10-06 14:53:51 UTC 

Answer 7

Try this, it works in Ruby:

 DateTime.now.to_time.utc