Converting unix timestamps in Ruby

Unix timestamps are common to see in other languages, and also common to see in API responses. Converting a unix timestamp to DateTime in Ruby is dead simple:

unix_timestamp = Time.now.to_i
# => 1453667949
DateTime.strptime(unix_timestamp.to_s, "%s").to_s
# => "2016-01-24T20:39:09+00:00" 

Let’s say your unix timestamp includes milliseconds:

unix_timestamp = (Time.now.to_f * 1000).to_i
# => 1453667949151
DateTime.strptime(unix_timestamp.to_s, "%Q").to_s
# => "2016-01-24T20:39:09+00:00" 


DateTime.strptime will allow you convert just about any formatted time string, see the docs for examples.

Notice how both DateTime strings are the same? DateTime converted to string drops any millisecond data, but keep it as a DateTime object and you can run strftime and display it in any format you like:

DateTime.strptime(unix_timestamp.to_s, "%Q").strftime('%D %T:%L')
# => "01/24/16 20:39:09:151"