datedebug.rb

Time.utc(1999, 12, 30, 23, 45, 00, 123000).strftime("%L")   # => "123" 
Time.utc(1999, 12, 30, 23, 45, 00, 123000).strftime("%3N")  # => "123"          millisecond (3 digits)
Time.utc(1999, 12, 30, 23, 45, 00, 123000).strftime("%6N")  # => "123000"       microsecond (6 digits)
Time.utc(1999, 12, 30, 23, 45, 00, 123000).strftime("%9N")  # => "123000000"    nanosecond (9 digits)
Time.utc(1999, 12, 30, 23, 45, 00, 123000).to_f             # => 946597500.123
Time.utc(1999, 12, 30, 23, 45, 00, 123000).usec             # => 123000

require 'date'
require 'rational'
require 'active_support'

Time.utc(1999, 12, 30, 23, 45, 00, 123000).strftime("%L")   # => "L" 
Time.utc(1999, 12, 30, 23, 45, 00, 123000).strftime("%3N")  # => "3N"
Time.utc(1999, 12, 30, 23, 45, 00, 123000).strftime("%6N")  # => "6N"
Time.utc(1999, 12, 30, 23, 45, 00, 123000).strftime("%9N")  # => "9N"
Time.utc(1999, 12, 30, 23, 45, 00, 123000).to_f             # => 946597500.123
Time.utc(1999, 12, 30, 23, 45, 00, 123000).usec             # => 123000


msec = 123
sec = 20
rat = sec + Rational(msec*1000,1000000)

class DateTime
  def usec
    (sec_fraction * 60 * 60 * 24 * (10**6)).to_i
  end
end

DateTime.civil(1999, 12, 30, 23, 45, 0)                       # => Thu, 30 Dec 1999 23:45:00 +0000
DateTime.civil(1999, 12, 30, 23, 45, 0).sec_fraction.to_f     # => 0.0
DateTime.civil(1999, 12, 30, 23, 45, rat)                     # => Thu, 30 Dec 1999 23:45:20 +0000
DateTime.civil(1999, 12, 30, 23, 45, rat).sec_fraction.to_f   # => 1.42361111111111e-06
DateTime.civil(1999, 12, 30, 23, 45, rat).usec                # => 123000