Understanding Time Zones – Dev Community

Before let’s talk about timezones, here’s what you need to know:

  • Latitude – imaginary horizontal lines on the Earth’s surface
  • longitude – imaginary vertical lines on the surface of the earth

Now back to the topic, with the latitude/longitude being clear.


A timezone is a region/region that experiences the same amount of time. This means that if you travel for a long time, you will not experience any change in time zone

How are time zones formed?

The Earth rotates at the equator at 1000 miles per hour.
Earth’s rotation is directly related to our time. So if we calculate, the earth rotates about 15 degrees every hour.
This means that the total number of hours in a day is 24 hours.

360/15 = 24 hours

If you look from the top-view (north-pole) you will see a line passing through the north-pole. One of its sides is called the prime meridian and the other is called the international date line.

Prime Meridian and International Dateline

If we go to the western hemisphere we have to subtract 1 hour for every 15 degrees and vice versa.

Prime Meridian and International Dateline

So if its at 12 o’clock on the prime meridian then it will be at 12 noon on the international dateline.

Names are given to each time zone and we call it IST, PST, PDT etc. There is no time difference between GMT and UTC, Before 1972, this time was called Greenwich Mean Time (GMT), but is now called Coordinated Universal Time or Coordinated Universal Time (UTC).

Also there are political changes made to the time zone value, i.e. some countries prefer to live in other time zones to keep things less complicated and more maintainable.

So now I hope you have got a good idea about the time zone. Now you can get some help using Date Constructors etc…

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