Example One

Step # 1
Mystery Class #1 sunrise time is given as 20:37 P.M. (UT/GMT) on March 19. This means it is late evening in Greenwich on the preceding day, March 19, when the sun rises on March 20 at this site.

BOX A

20:37 P.M.
(3/19)
Step # 2
Sunrise time at Greenwich on March 20 is 06:02 A.M.
BOX B

06:02 A.M. (3/20)
Step # 3
The number of hours and minutes between A and B is 9 hours and 25 minutes

BOX C

9 hrs 25 min
Step # 4
Convert the amount of time in Box C into minutes by multiplying the hours by 60 and adding the remaining minutes
(9 x 60 = 540 + 25 = 565 minutes)

BOX D

565 minutes
Step # 5
Figure out the degrees away from Greenwich by dividing the minutes in Box D by 4 (565 divided by 4 = 141.25 degrees)


BOX E

141.25 degrees
Step # 6 Eastern or Western Hemisphere?
To determine the site's approximate longitude you need to know if it is in the Eastern or Western Hemisphere (i.e east or west of Greenwich, which is 0 degrees). Here, 20:37 P.M. on 3/19, the preceding day,was earlier than 06:02 A.M. on 3/20, so this longitude location is East.

This means the site is east of Greenwich, in the Eastern Hemisphere.

BOX F

141.25 E