#time_unit__unit_of_time  a unit for measuring time periods
  supertype:  pm#unit_of_time_duration (pm)  #unit_of_measurement
  subtype:  #day__meansolarday__twenty-four_hours__solar_day  time for Earth to make a complete rotation on its axis; "two days later they left"; "they put on two performances every day"; "there are 30,000 passengers per day"
  subtype:  #night.time_unit  the dark part of the diurnal cycle considered a time unit; "three nights later he collapsed"
  subtype:  #mean_time__mean_solar_time  (astronomy) time based on the motion of the mean sun (an imaginary sun moving uniformly along the celestial equator)
  subtype:  #terrestrial_time__terrestrialtime__tt__terrestrial_dynamical_time__terrestrialdynamicaltime__TDT__ephemeris_time__ephemeristime  (astronomy) a measure of time defined by Earth's orbital motion; terrestrial time is mean solar time corrected for the irregularities of the Earth's motions
  subtype:  #month  a time unit of 30 days; "he was given a month to pay the bill"
     subtype:  #lunar_month__moon__lunation__synodic_month__synodicmonth  the period between successive new moons (29.531 days)
     subtype:  #anomalistic_month  period between successive perigees; approximately 27.5546 days
     subtype:  #sidereal_month  period between successive conjunctions with a star, 27.322 days
     subtype:  #solar_month__solarmonth  one-twelfth of a solar or tropical year
  subtype:  #sidereal_day__day  the time for one complete rotation of the earth relative to a particular star, about 4 minutes shorter than a mean solar day
  subtype:  #ship's_bell__bell  (nautical) each of the eight half-hour units of nautical time signaled by strokes of a ship's bell; eight bells signals 4:00, 8:00, or 12:00 o'clock, either a.m. or p.m.
  subtype:  #hour__hr__60_minutes  a period of time equal to 1/24th of a day; "the job will take more than an hour"
     subtype:  #sidereal_hour  1/24 of a sidereal day
     subtype:  #man_hour__manhour__personhour  a time unit used in industry for measuring work
  subtype:  #half-hour__30_minutes  a half of an hour
  subtype:  #quarter-hour__quarterhour__15_minutes  a quarter of an hour
  subtype:  #minute__min  a unit of time equal to 60 seconds or 1/60th of an hour; "he ran a 4 minute mile"
  subtype:  #quarter.time_unit  a unit of time equal to 15 minutes or a quarter of an hour; "it's a quarter til 4"; "a quarter after 4 o'clock"
  subtype:  #second__s____sec  1/60 of a minute; the basic unit of time adopted under the System International d'Unites
     subtype:  #leap_second  a second (as measured by an atomic clock) added to or subtracted from Greenwich Mean Time in order to compensate for slowing in the Earth's rotation
  subtype:  #millisecond  one thousandth of a second
  subtype:  #attosecond  one quintillionth of a second; one thousandth of a femtosecond
  subtype:  #femtosecond  one quadrillionth of a second; one thousandth of a nanosecond
  subtype:  #picosecond  one trillionth of a second; one thousandth of a nanosecond
  subtype:  #nanosecond  one billionth of a second; one thousandth of a microsecond
  subtype:  #microsecond  one millionth of a second; one thousandth of a millisecond

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