An [Acronym] for __U__niversale __T__emps __C__oordineé, ie Coordinated Universal Time. 

  

 This is the standard time zone all other time zones are based on. It replaced [GMT] in the early 1970s. [UTC] is measured with atomic clocks. It is kept within 0.9 seconds of [TAI], but with an integral number of leap seconds added occasionally to reflect the season at and location on the planet. This way [UTC] stays in sync with the rotation of the earth, making sure midnight always occurs at the same time relative to the stars. To date all corrections have been positive to account for the tidal drag on the earth which slows the planet down.