Subject: Social Studies
You know Nepal lies between 80°E and 88°E longitudes. So time difference within Nepal in as much as 32 minutes(1°= 4 minutes). The time calculated on the basis of the distance between prime meridian and the longitude of a certain place in known as local time. For convenient time relations, we need to have an average time that can be applied throughout the country. 84°E would be the exact average longitude for Nepal. As a practice we have taken 86° 15' E longitude passing through Dolakha as such meridian. The same is the standard meridian of Nepal. We have to see the relation between this longitude and the prime meridian. When we measure Nepal's standard time from the prime meridian, It is 5 hours and 45 minutes (86.25° 4 minutes= 345 minutes) ahead of the GMT. This in the standard time for Nepal. When a country covers two or more time zones, there are more standard times applied within the country. For example, Canada has 4 different time zones. But China, though large, uses a single time zone. This is rare.
Now you know every 15 ° eastwards the time is 1 hour later. The time in Helsinki (25°E) is nearly 2 hours ahead of that in London (0°). So when it is 2 pm in London, it in nearly 4 PM in Helsinki. Similarly it in nearly 8 PM in Kathmandu (85°E). Then how far are Rio de Janeiro and Riyadh in their longitudinal extent and time difference? See their positions first.
Longitudinal distance between Rio de Janeiro and Riyadh = 43°W+ 47°E = 90°
We add their distances from the Prime Meridian because they extend in two opposite directions; west and east from the Prime Meridian. In other words, they lie in two opposite hemispheres.
How far are they in their time distances?
|We know every 1°= 4 minutes. |
So these two places are 90*4= 360 minutes or 360/60 =6 hours far apart.
Note that the longitudinal different between Port-au-Prince and Rio de Janeiro in 73°-43°W = 30° because both places lie in the same hemisphere.
The time eastwards is faster because the earth moves from west to east and eastern part receives early sunlight.
10 longitude is equal to 4 minutes the round earth measures 3600 and ot takes 24 hours (1440 minutes) to complete one rotation.
Even after it is dusk in Jhapa, the sun is shining in Kanchanpur because Kanchanpur lies nearly 80 westward from Jhapa and time they are in 32 minutes back. (In other words time in Jhapa is 32 minutes faster than in Kanchanpur )
Current time in London = 2 pm
Current time in Dhaka = 8 pm
Current time in Manila = ?
150 eastward = 1 hour later
We know, longitudinal position of London = 00
longitudinal position on manila = 1200 (approximately)
longitudinal distance between London and manila = 1200 -00 = 1200
Time distance between the places = 120/ 15 = 8 hrs (150 = 1hour)
∴ current time of Manila = current time of London + Time distance
= 2pm + 8 hour
When it is 2 pm in London and 8 pm in Dhaka, the clock in Manila strike 10 pm.
Longitude of our place ( Kathmandu) = 850 E
Current time of Kathmandu = 12 pm
Longitude of Greenwich = 0 0
Greenwich Meantime =?
Now, longitudinal distance between two places = 850 – 00 = 850
Time distance = 850 x 4 minutes (10 = 4 minutes)
= 340 minutes
=5 hour 40 minutes
∴ current time of Greenwich = 12: 00 pm – 5: 40 hrs
= 6 :20 am
When it is midday in Kathmandu, it is early morning in Greenwich.
Longitude of Tashkent = 700 E
Longitude of Chicago = 870 W
Current time of Chicago = 6:00 am
Current time of Tashkent = ?
Now, longitudinal distance between the two places = 700 + 870 = 1570
(Because Tashkent and Chicago lie in two different hemispheres)
Time distance = 1570 x 4 minutes (10 = 4 minutes)
= 628 minutes
=10 hours 28 minutes
∴current time of Tashkent = 6: 00 am + 10 : 28 hrs
= 4:28 pm
(Here time distance is added because Time of Tashkent which lies in the east is to be calculated)
Longitudinal position of New York = 740 W
Longitudinal position of my place = 840 E (pokhara)
Current time of Pokhara = 10:00 am
Current time of New York =?
Now, longitudinal distance between New York and Pokhara = 740 + 840
Time distance between the tweo places = 1580 x 4 minutes
=10 hours 32 minutes
Current time of New York = current time of pokhara – time distance
= 10:00 am – 10:32 hrs
(Here 12 hour are added to 10:00 am to make easy subtraction and the figure subtracted thus is changed into am)
Here, time of Bagdad = 4 pm
Time of Singapore = 8 pm
Longitudinal of Bagdad = 440 E
Longitudinal of Singapore = ?
Now, time distance Bagdad and Singapore = 8 pm – 4 pm = 4 hrs
Longitudinal distance between Bagdad and Singapore = 440 E + 600
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