CURRENT AFFAIRS FOR UPSC IAS

Working of Earth’s Time Standard

• Time Zones are a geographical world globe division of 15^o each, starting at Greenwich, in England, created to help people know what time is it now in another part of the world.
• The local time within a time zone is defined by its offset (difference) from Coordinated Universal Time (UTC), the world's time standard.
  • UTC is essentially an internationally agreed upon standard for world time.
• It is tracked by a weighted average of more than 400 atomic clocks placed in different parts of the globe.
• Atomic clocks measure time in terms of the resonant frequencies — the natural frequency of an object where it tends to vibrate at a higher amplitude — of atoms such as cesium-133.
  • In atomic time, a second is defined as the period in which a caesium atom vibrates 9,192,631,770 times. As the vibration rates at which atoms absorb energy are highly stable and ultra-accurate.
• UTC time changes 1 hour forward and backward corresponding to a 1-hour difference in mean solar time for every 15 degrees east or west of the prime meridian (0° longitude) in Greenwich, London, United Kingdom.
• The offset is expressed as either UTC- or UTC+ and the number of hours and minutes.