General Knowledge - Time Line


  • Parallels of longitude determine the time of a given place.

  • Local time (of any place) is measured in reference to Greenwich Time (London), which changes at the rate of four min/degree of longitude.

  • Greenwich Time Line is also known as “Prime Meridian” i.e. 00.

  • International Standard Time is measured in reference of the Prime Meridian (or Greenwich).

  • The Earth rotates through 3600 in 24 hours or 150 in 1 hour or 10 in 4 minutes. Therefore, the local time varies at the rate of 4 min/degree of longitude from the Greenwich Time.

Time Line
  • As shown in the map given above, Kolkata is approximately 900 east of Greenwich; so, Kolkata is (900 x 4 = 360 min) six hours ahead of the Greenwich Time (London).