What is the time and day at certain place on 60° W longitude when it is 5.30 a.m. on Friday at a place 90° east longitude?

• The longitudinal difference: 60° + 90° = 150°
• For 1° longitudinal difference time difference is 4 minutes.
• So, for 150° longitudinal difference, the time difference is 150° x 4 = 600 minutes or 10 hours.
• As the given place is situated in the west of 90° east longitude, the local time at 60° west will be: (5:30 a.m. - 10 hours) = 7:30 p.m. on Thursday.