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Topics in Local Time Computing

Local time, zone time exercises

First, the calculation of relevant places

1. When the longitude of A and B and the place of A are known, find the place of B: the place of B = the place of A +

If B is on the east of A, use "+"; if B is on the west of A, use "-".

Example 1: When the place at 115 ° east longitude is 9:30, what is the place at 125 ° east longitude?

Analysis: Because the longitude of 125 ° is located to the east of 115 ° of the longitude, the longitude difference is 4 minutes 01

1250 1150

At 125 ° east longitude = 9:30 + (4) minutes = 9:30 + 40: 10:10, 01

That is to say, when the longitude of 115 ° is 9:30, the longitude of 125 ° is 10:10.

Example 2: The time at place A is 120 ° east longitude at 10:20, and the place B is 90 ° east longitude. Find the place of place B.

1200 900

Analysis: Because B is on the west side of A, so: When the place is B = 10: 20-4 minutes 01

= 10: 20-120 minutes = 8: 20

2. Know the place of two places and the longitude of one place, find the longitude of the other place

Required longitude = known longitude ± local time difference 0 1 4 minutes

example 1. When London is noon and the city is at 20:00, the time is ()

A. Sydney (150 ° E) B. Shanghai (120 ° E)

C. Los Angeles (120 ° W) D. Accra (near 0 ° meridian)

Analysis: London is 12:00 at noon and longitude is 0 °; while the place at 20:00 should be in the east of London, then:

Local time difference 0 1 4 minutes

20 120 = 0 ° + 1 4 Longitude sought = known longitude ±

= 120 ° E

Calculation of time zone and zone time

1. Given the time zone of A and B and the time zone of A, find the time zone of B:

Time in area B = time in area A ± time zone difference

If B is on the east of A, use "+"; if B is on the west of A, use "-".

When the calculation result is less than 24, then the date does not change, and the time takes the calculation result;

When the calculation result is greater than 24, the date is increased by 1 day, and the time is calculated by 24.

The calculation result is negative, then the date is subtracted by 1 and the time is calculated by adding 24;

1 hour for each time zone passing from east to west; crossing the date line (180 meridian °), plus 1 day for the date;

Every time zone from west to east is added by 1 hour; the date is reduced by 1 day after crossing the solar boundary (180 meridians).

2 travel time calculation:

Find the arrival time from the departure time, plus the travel time;

From the arrival time to the departure time, the travel time must be subtracted.

Note: The direct solar point is at zero meridian, the same day worldwide.

example 1. At 19:00 local time on the eve of Christmas (December 25), a match of the English Premier League will start in London. Mr. Lee from Hong Kong is going to London to watch the game. The flight time from Hong Kong to London is about 17 hours. Try to answer the following questions.

(1) At the start of the match, China's Beijing time should be

Analysis: A: London (Central Time Zone) at 19:00 on December 24th, B: Beijing (East Eight), time zone difference = 8, B is located east of A, so when calculating eastward:

Time in area B = time in area A + time zone difference = 19:00 + 8:00 = 27:00

Then: the date is December 24th + 1st (December 25th), and the time is 27: 00-24: 00 = 3: 00

That is, the corresponding Beijing time at the start of the game is 3:00 on the morning of December 25

(2) Among the following Hong Kong-London flight departure times, Mr. Li chooses more appropriately.

A. B. 15:00 on the 23rd B. 18:00 on the 23rd 7:00 am on the 24th 10:00 on the 24th

Analysis: This is based on the arrival time to find the departure time, and then subtract the travel time from the above calculation results:

Departure time = Area A + Jet lag-Travel time

= 19:00 + 8: 00-17: 00

= 10:00

That is to say, Mr. Li should have departed at 10:00 on December 24th, but it is impossible to watch the game from the plane. Some necessary preparations must be made, such as dining, driving to the stadium, etc., should be on the 24th at 10: 00 Beijing time Departure before 00. So choose C.

Example 2. When New York (Western Fifth District) is at 12:00 on April 30, Beijing should be ()

A. B. April 30, 1 B. B. 1 May 1 A. April 29th, D. 9:00 on May 1

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