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Time.mktime/iso8601 off by millisecond |
Time class in Ruby has the following interesting behaviour when using iso8601 with fraction digits:
Time.mktime(2013, 11, 2, 21, 27, 16.424).iso8601(3)
=> "2013-11-02T21:27:16.423+00:00"The result is off by one millisecond.
Because this is essentially a floating-point rounding problem, the safest and most eloquent way to solve this is to use Rational.
This also helps when converting timestamps with milliseconds (the likes Java gives, for example), and avoid any problems when representing
it:
Time.mktime(2013, 11, 2, 21, 27, Rational(16424, 1000)).iso8601(3)
=> "2013-11-02T21:27:16.424+00:00"This can also be worked around by using either a non-zero additional millisecond digit in mktime, or
using the round function before iso8601 or using to_f and Time.at:
Time.mktime(2013, 11, 2, 21, 27, 16.4241).iso8601(3)
=> "2013-11-02T21:27:16.424+00:00"
Time.mktime(2013, 11, 2, 21, 27, 16.424).round(3).iso8601(3)
=> "2013-11-02T21:27:16.424+00:00"
Time.mktime(2013, 11, 2, 21, 27, 16.424).to_f
=> 1383427636.424
Time.at(1383427636.424).iso8601(3)
=> "2013-11-02T21:27:16.424+00:00"This behaves the same in Ruby 1.9, 2.0, and 2.1.