Units.create :time do |m|
  m.system :base do |s|
    s.unit :name => :nanosecond, :equals => 0.000000001.seconds,
      :abbrev => [:ns, :nsec]
    s.unit :name => :microsecond, :equals => 0.000001.seconds,
      :abbrev => [:us, :usec]
    s.unit :name => :millisecond, :equals => 0.001.seconds,
      :abbrev => [:ms, :msec]
    s.unit :name => :second, :abbrev => [:s, :sec]
    s.unit :name => :minute, :equals => 60.seconds, :abbrev => [:m, :min]
    s.unit :name => :hour, :equals => 60.minutes, :abbrev => [:h, :hr]
    s.unit :name => :day, :equals => 24.hours, :abbrev => [:d, :dy]
    s.unit :name => :week, :equals => 7.days, :abbrev => [:w, :wk]
    s.format :name => :weeks_and_days,
      :format => lambda { |u|
                          weeks = u.weeks.floor
                          days = (u-weeks).days.round
                          weeks == 0 ?
                             (days == 0 ? "#{weeks}" : "#{days}") :
                             "#{weeks} #{days}" }
  end
  m.system :common do |s|
    s.unit :name => :month, :equals => [30.days, 4.weeks], :abbrev => [:m, :mo]
    s.unit :name => :year, :equals => [365.days, 12.months, 52.weeks],
      :abbrev => [:y, :yr]
  end
  m.system :long do |s|
    s.unit :name => :decade, :equals => 10.years
    s.unit :name => :century, :plural => :centuries, :equals => 100.years
    s.unit :name => :millenium, :plural => :millenia, :equals => 1000.years
  end
  m.system :old_english do |s|
    s.unit :name => :fortnight, :equals => 2.weeks
  end
  m.system :months do |s|
    s.unit :name => :january, :equals => 31.days, :singular => true,
      :sequence => 1
    s.unit :name => :february, :equals => [28.days, 29.days], :singular => true,
      :sequence => 2
    s.unit :name => :march, :equals => 31.days, :singular => true,
      :sequence => 3
    s.unit :name => :april, :equals => 30.days, :singular => true,
      :sequence => 4
    s.unit :name => :may, :equals => 31.days, :singular => true,
      :sequence => 5
    s.unit :name => :june, :equals => 30.days, :singular => true,
      :sequence => 6
    s.unit :name => :july, :equals => 31.days, :singular => true,
      :sequence => 7
    s.unit :name => :august, :equals => 31.days, :singular => true,
      :sequence => 8
    s.unit :name => :september, :equals => 30.days, :singular => true,
      :sequence => 9
    s.unit :name => :october, :equals => 31.days, :singular => true,
      :sequence => 10
    s.unit :name => :november, :equals => 30.days, :singular => true,
      :sequence => 11
    s.unit :name => :december, :equals => 31.days, :singular => true,
      :sequence => 12
  end
end