Time Zones and International Date Line!

   

    Time zones are the type of zones in which times are followed up differently in each zone; which means, that countries in each zone follow different times. For example, if we are in India where the time is 5:30 PM Friday then the time in London will be 12:00PM Friday. Even more interesting is that, if we are in India where the time is 9:30PM Thursday, and travelled along westwards to Abu Dhabi within 1 hour with a high-speed jet, then the time will be still at 9:30PM Thursday as before. So we have no loss of time. This is the magic of Time Zone!

Time Zones of Earth

    There are roughly 24 time zones in the world corresponding to the 24hr in the world. But some countries make a quarter and a half an hour offset; due to which there are more than 24 time zones in the world. These time zones are determined by the longitudinal lines around the earth that are separated by 15° corresponding to 1 hour. Each longitudinal line is called standard meridians. There are 24 standard meridians in the world. The first meridian where the time starts is called the prime meridian. From this prime meridian, all other countries make their own time zones by making offsets. The time zone for the country is set by the respective longitudinal line. For each longitudinal line 1 hour increases on the east and one hour decrease on the west to the prime meridian.  For example, the country that falls on the first longitudinal line on the east to the prime meridian will have 1:00PM, if the prime meridian has 12:00PM. Similarly, the country that falls on the first longitudinal line on the west to the prime meridian will have 11:00AM, if the prime meridian has 12:00PM.

Time Zones of Earth with respect to Prime Meridian

    The prime meridian is the longitudinal line that falls in London, UK. So this place follows the Coordinated Universal time (UTC) or Greenwich Mean Time (GMT); which means, it follows the base time for all over the world. By keeping this time as a base, all other country alters their time. There are also some other places, that fall on this longitudinal line, which follows too the UTC time. Those places are Accra, Valencia, Bordeaux, and many more.

    The word offset means, the difference in time from the universal time (UTC). Let’s take the country India for example. If we have to say the timing of this country with respect to the country's time, we can say it as 3:00 PM IST (This timing is an example). Here the IST denotes the country’s time zone and the time 3:00 PM denotes the country’s local time. This local time will be compatible with the people in India. But for the world, the time of India is said with respect to the global time (UTC) as UTC+5:30 which means that the time followed in the prime meridian region must be added with 5 hours and 30 minutes to give the timing of India. This +5:30 is called the offset of UTC. Each country has its own offset from UTC to denote its own local time. For example, the country Oman uses +4:00 while the time at Bolivia is -4:00, which means four hours will be subtracted from the UTC, while in Oman four will be added to the UTC to give Oman’s local time. Most countries will have the offset as a whole number as 6 hours or 7 hours. But some countries like India and Sri Lanka use an additional half an hour offset which tends to increase the number of time zones in the world. Even some country like Nepal uses three-quarters offset (3/4) as UTC+5:45.

Prime Meridian (Difference between Universal time and local time)

     Even though both the UTC and GMT are at the same time, there is a slight difference between them. First of all, GMT is a time zone whereas UTC is a time standard. A Time zone is a particular time that is followed by a particular country; so that each country will have a different particular time making as their time zone. Whereas UTC is the universal time, which means by keeping this time base all other country alters their time. So no country keeps UTC as their time zone but mentions their time either as UTC+ (their offset time) or by their own time zone such as IST or BST etc. So the countries that lie on the UTC line will name their time zone as GMT like IST or BST. For example, London will say their time as 12:00PM GMT and not UTC. But both GMT and UTC follow the same time. There is no time difference between them.

    So by keeping the UTC as the baseline, many countries adopt their own time zones by creating an offset or by mentioning it with a different name. Let’s see the names of some countries' time zones.

• India- Indian Standard Time (IST)

• Israel- Israel Standard Time (IST)

• Albania- Central European Time (CET)

• Bangladesh- Bangladesh (BST)

    While some countries use only one time zone for their entire country for their sophistication, others use various time zones; as the country crosses several longitudinal lines, which makes it a necessity for having several time zones. For example, countries like Russia and the United States use 11 time zones, to have precise timing all over the country. Even though countries cross several time zones, countries like China use only one time zone, even if it crosses several time zones.

    Another important thing that should be considered in the time zone is the day losing and gaining. There is a line in the globe that marks the end of the day for the world. The line is called the International Date Line. If anything on the earth crosses the line the day changes; as the earth rotates in an anticlockwise direction (i.e., west to east). So the portion west to the International Date Line will be on a day advance to the day on the east portion of the International Date Line. For example, when the west portion from midnight is on Monday, the east portion till midnight will be on Sunday. So if a person crosses the International Date Line from west to east he will gain a day and when he crosses from east to west he will lose a day.

 

Concept of International Date Line