# Practical exercise 1: TIME ZONES

## Tools

map of the Slovak Republic, world map, time zone map – for example https://upload.wikimedia.org/wikipedia/commons/8/88/World_Time_Zones_Map.png

## Process

1. Find on the map of the Slovak Republic some city that lies at the 15th meridian of eastern longitude. Next, find the easternmost point and the westernmost point. Determine their geographic coordinates.

(Answer: for example, Pacov 49° 28'; 15° 06'; the easternmost point 49° 55'; 18° 52'; the westernmost point 50° 15'; 12° 05')

2. On the 15th meridian, the sun rises on a certain day at 6.00 am and sets at 6.00 pm. At what time does the sun rise and set in the easternmost and westernmost place of the Slovak Republic? Neglect the altitude of the place and its surroundings.

(Answer: The difference in longitude between the easternmost place in the Czech Republic and the 15th meridian is 3° 52', between the westernmost place in the Czech Republic and the 15th meridian it is 2° 55'. Because a 15° longitude difference means a difference of 1 hour (360 degrees mean 24 hours), a 1° longitude difference means a 4 minute difference. In the easternmost place of the Czech Republic, the sun rises and sets 15.5 minutes earlier, in the westernmost place 11.5 minutes later.)

3. Find a place on the map where the sun rises on the same day at 5.50 am.

(Answer: A difference of 10 minutes means a difference of 2.5° longitude from the meridian of 15°. The sought-after place therefore lies at the meridian of 17.5°. For example, the town of Tlumačov is located on this meridian.)

4. The sun set in Plzeň at 4.16 pm. What time did the sun set in Žďár nad Sázavou? Neglect the altitude of both places and their surroundings.

(Answer: Plzeň 49° 44'; 13° 23'; Žďár nad Sázavou 49° 34'; 15° 56'; the longitude difference is 2° 33'. The sunset time difference is 10.2 minutes. The sunset took place in Žďár nad Sázavou at 4.06 pm.)

5. There is a 6:00 am time in Prague on December 3. What is the date and time in Tokyo, Sydney, Cairo, Ottawa?

(Answer: Tokyo lies in a time zone with 9 hours difference from universal time. There is 8 hours more than in Prague, i. e. December 3 2 pm. Similarly, in Sydney (+ 10 hours compared to universal time), it is 3 pm. It is 7 am in Cairo (+ 2 hours). Ottawa is located in a zone with a time less than 5 hours from universal time. There is therefore 6 hours less than in Prague, so it is midnight from December 2 to 3.)

6. For time zones, it is often simply stated that the Earth is divided into 12 zones delimited by meridians with a bandwidth of 15 degrees, in which the time zone is given by the time of the meridian