Also known as the Local Mean Time (LMT), it is a kind of solar time. In other words, it is one of the methods of calculating and keeping the duration of time by observing the sun’s location in the sky.
It differs from the standard time insofar as a country’s law determines the latter, keeping in mind the distance of the central meridian of that country from the Prime Meridian (0° Longitude).
In contrast, Local Mean Time is region-specific and depends on the sun’s position over the meridian running through that region.
Until the late nineteenth century, local mean time was used to determine the clocks of a region. The tool used to determine a place’s local mean time was called sundial.
However, with the railways becoming a predominant means of transport during the late nineteenth century, a uniformity of time became the need of the hour. The railways’ administrators could not prepare a uniform train schedule with different stations following different time clocks. Faced with this dilemma, the officials introduced the concept of a standard time.
- Local time is the time observed within a specific geographic region based on its position relative to the Earth’s longitudinal lines.
- Each time zone spans 15 degrees of longitude, with the Prime Meridian (0 degrees longitude) as the reference point for Coordinated Universal Time (UTC).
- Daylight Saving Time (DST) is implemented in various countries to better use daylight by adjusting the clock one hour forward or backward, resulting in a temporary shift in local time.
How does Local Time work?
It is well-known that the earth rotates from west to east upon its axis. Consequently, the sun seems to set in the west and rise in the east.
However, not all parts of the earth experience daylight simultaneously. It takes 24 hours for the Earth to complete a rotation of 360 degrees. In other words, the earth traverses 15 degrees in one hour or one degree in four minutes.
Consequently, the earth has been divided into 24 time zones, with each of them being 15 degrees apart from each other.
The rate of time at which the sun moves over a specific degree of longitude sets a region’s local time about the Prime Meridian.
For example, the local time of Bhutan (Thimpu), which is located at 90° longitude to the east of the Prime Meridian, will be 6 pm if it is noon at the Greenwich Meridian (0°) as the time difference between them is of 6 hours.
Similarly, there will be considerable differences between the local time of New Delhi, located at 77.21° E, and Silchar, located at 92.78° E.
Advantages of Local Time
Even though the usage of local time has become almost obsolete in contemporary times, it has some indirect advantages.
- Synchronization with the earth’s rotation: It allows us to synchronize our clock with the earth’s rotation.
- UT 1: The UT1, a version of the Universal Time, used as one of the reference points for determining the standard time of all other countries, is the local time of the Greenwich Meridian.
- Provides the precise time for time-bound activities: It gives us an idea of the exact time for a particular location which is essential to schedule specific time-bound activities like transportation.
- Astronomers’ friend: Astronomers worldwide depend on the local mean time (LMT) to enunciate their observations.
- Dictates people’s daily activities: Despite the standard time determining a country’s time clock, the local time regulates people’s day-to-day activities.
Disadvantages of Local Time
Local Mean Time was not given up for no reason during the late nineteenth century. The following are some significant drawbacks of the local time:
- Prevents administrative uniformity: It is a significant obstacle in establishing it.
- Generates a lack of coordination: It creates a lack of coordination regarding the economic exchange between different cities, villages, and regions.
- Generates chaos: It creates too much confusion from the administrative point of view.
- Temporal differentiation and its impact on the residents’ cognition: It creates a sense of difference among the people living in different time zones.
- Obstructs national integration: Too many time zones act as a blockade in the path of national integration.
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Piyush Yadav has spent the past 25 years working as a physicist in the local community. He is a physicist passionate about making science more accessible to our readers. He holds a BSc in Natural Sciences and Post Graduate Diploma in Environmental Science. You can read more about him on his bio page.