Monkey patch for broken Time.at in JRuby 1.7.3

jruby_1.7.3_time_patch.rb

if RUBY_PLATFORM =~ /java/i
  # ruby-units monkey patches the Time class which in turn exposes a bug in
  # JRuby (https://github.com/jruby/jruby/issues/565)
  class Time
    class << self
      if defined?( Unit )
        # ruby units got there first
        alias agworld_ruby_time_at unit_time_at
        alias agworld_unit_time_at at
      else
        alias agworld_ruby_time_at at
      end
    end

    def self.at(arg, ms=nil)
      if defined?( Unit )
        # Unit existing implies ruby-units is loaded
        if arg.kind_of?( Unit )
          # call ruby-units' monkey patched Time.at, safe to pass through ms 
          # because ruby-units internally passes through to JRuby's Time.at with
          # a float as the first arg and not a Time (which avoids the bug)
          return agworld_unit_time_at( arg, ms )
        end
      end
      # otherwise always call to Ruby's original Time.at
      if ms.nil?
        return agworld_ruby_time_at(arg)
      else
        return agworld_ruby_time_at(arg + (ms*0.000001))
      end
    end
  end
end