The article gives a detail understanding of Different Times Zones and How to Calculate Local Time.
Our world is a sphere that revolves around an axis, which is an illusory pole. One full revolution of the Earth occurs every twenty-four hours. Let’s call one complete rotation a day. Consider illuminating a globe with a flashlight. It would only receive partial light. That side would be dark on the other. Day and night are created by the rotation of the Earth, which distributes sunshine and darkness throughout the planet. You watch the sun rise as your position on Earth spins into sunlight. You see the sun set when the position you are in rotates out of the sunlight.
Consider a world if there was only one time zone on Earth. In some areas, noon would be the middle of the day; in others, it would be the morning, the evening, or the middle of the night. We require distinct time zones because different portions of the Earth experience daylight at different times.
For a very long time, people have lived in different time zones, but it wasn’t always as structured as it is now. A little more than a century ago, cities and towns kept their own time. Every day at noon, when the sun was at its zenith, someone would ensure that the official town clock was set to that time. After that, they would walk around the community adjusting clocks of other individuals to ensure they matched.
This became increasingly complex, as the world grew more interconnected. With the advent of train travel across North America, it became increasingly challenging to keep track of the several time zones. There was a time when rail stations in the US alone had to adjust to 75 different time zones.
The Earth travels around 15 degrees every 60 minutes as it turns on its axis. It has turned around completely 360 degrees after a whole day. Using this data, the scientists created 24 time zones or portions of the world. The width of each time zone is 15 degrees longitude.
At the equator, the distance between the zones is at its largest. Due to Earth’s curvature, it decreases to zero near the poles. The distance between time zones at the equator is around 1,038 miles since the equator is roughly 24,902 miles long.
The fictitious border starts in the London neighbourhood of Greenwich. The prime meridian is the principal longitude dividing line. The angular separation between a location on any meridian and the prime meridian at Greenwich is known as longitude.
Time Zones are mostly used to refer local time of a region. The local time within a time zone is defined by its offset (difference) from Coordinated Universal time (UTC) which is standard time of the world.
UTC time changes 1 hour forward/backward relating to 1 hour difference in mean solar time for every 15 degrees east/west of prime meridian which is also known as Standard Meridians. IDL creates 3 time zones and many time zones are 30 and 45 min apart, that’s why there are more than 24 time zones.
The International Meridian conference chose the royal observatory at Greenwich, London, England as the place of Prime Meridian i.e. 0° longitude.
There are many types of Time Zones:
- Day light Saving Time zone: Regions using DST change the time zone name and time during Summer period and keeps same for all remaining period.
For ex- California uses Pacific daylight time during DST while uses Pacific standard time during rest of the year. DST is used to make more use of summer daylight. So, it causes a lost hour of sleep in the spring and an extra hour of sleep in the Fall. It is not used near the equator, Asia, Africa do not observe it. UTC is standard time not time zone.
- Greenwich Time zone: It has no relation with UTC. This time zone is in the use during
standard time in Europe, Africa, North America, Antarctica.
Australia, New Zealand, South Africa, Eastern Hemisphere, India, Greenland ad Iceland uses GMT all year. It is mean solar time reckoned from midnight. Noon GMT is the average moment of the event.
- Flying Time: It is the time spent in the sky or in the aircraft during flying.
For example-
- Elapsed Time: It is the extra time taken by the aircraft over flying time for some emergencies or un-avoidable situations.
- Grounding Time: The total time taken by the aircraft from landing to next takeoff.
- Journey Time: It is the total time taken by the aircraft including flying time and elapsed time.
How to Calculate Local Time:
We will learn to calculate local time by given below example:
The longitudinal value of New Delhi is 82.5° E (82.5° behind Prime Meridian). As said earlier, each 15° longitude constitutes one hour difference in time zone. Hence, the hour difference from Prime Meridian can be calculated as a longitudinal value divided by 15° i.e., 82.5°/15 = 5.5 hours. This means New Delhi is 05 hours and 30 minutes ahead of Prime Meridian since New Delhi is located East of Prime Meridian. Sun rises in the East, hence location in East is ahead of Prime Meridian while west is behind Prime Meridian.
As time moves eastwards from the prime meridian, with every standard meridian there is an addition of 01 hour in the time. If it is 12 noon at Prime Meridian, the time at the first standard meridian on the right will be 1 pm. Similarly, when it moves towards the west, 1 hour decreases with each standard meridian. When it is 12 noon at the prime meridian, the first standard meridian on the west shows the time as 11 am. The sign + (plus) and -(minus) are used to mention the time relative to GMT/UTC.
- GMT+1 =1 Hour ahead of GMT (Towards the east of GMT)
- GMT-1 =1 Hour behind GMT(Towards west of GMT) up to GMT +12 and GMT-12.
Question: What is the time in Calcutta (96 ͦ east) when it is 09:00 a.m. in Munich (11 ͦ east)?
Also Read:
- Different Environment and Wildlife Acts in India Tourism Sector
- 3 Major Distribution of Physical Geography of India
- 6 Major Types of Climate and Climate Zone in the World
– The longitude difference is (96-11) ͦ east which will be 85 ͦ east.
Now we know that for 1 hour, there is shift of 15 ͦ so for 85 ͦ, the time will be 85/15 equals to 5 hr. 40 min. Calcutta is east of Munich.
So, adding 09:00 + 5 hr. 40 min will result in 14 hr. 40 min (in Calcutta).
