[ruby] How do I Convert DateTime.now to UTC in Ruby?

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

DateTime.now.new_offset(0)

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

Unfortunately, the DateTime class doesn't have the convenience methods available in the Time class to do this. You can convert any DateTime object into UTC like this:

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

You can switch back from UTC to localtime using:

d.new_offset(DateTime.now.offset)

where d is a DateTime object in UTC time. If you'd like these as convenience methods, then you can create them like this:

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 initial DateTime object has a -04:00 offset (Eastern Time). I'm in Pacific Time with a -07:00 offset. Calling localtime as described previously properly converts the DateTime object into local time. Calling utc on the object properly converts it to a UTC offset.

Try this, works in Ruby:

DateTime.now.to_time.utc

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"

will convert the time to the utc. But as posted if it is just Time you can use:

Time.now.utc

and get it straight away.

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

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

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

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"