Gained Day

A ship sailing eastward meets the sun in his daily course, and in the circumnavigation of the globe the sun will have crossed the ship's meridian once more often than if the vessel had remained stationary; so it is that an easterly circumnavigator gains a day. On the other hand, a ship sailing westward runs away from the sun in his daily course, and in the circumnavigation of the globe the sun will have crossed the ship's meridian once less often than if she had remained stationary. The date is altered by adding or subtracting one day of the month on crossing the meridian of 180 deg.