Date Line is an imaginary north south line through the Pacific Ocean. The date changes when the line is crossed - east of the line is a day earlier than it is to the west.
In the travel, transport, and hotel context, "Date Line" refers to the imaginary line on the Earth's surface that separates two consecutive calendar days. The International Date Line (IDL) is an imaginary line on the Earth's surface that roughly follows the 180th meridian of longitude, and it is used to determine when a new calendar day begins.
For example, when traveling westward across the International Date Line, one will "lose" a day and when traveling eastward, one will "gain" a day. For example, if a person departs from New York City on January 31st, and arrives in Tokyo on February 1st, they have crossed the International Date Line and have "gained" a day.
This line is also important for travelers because of time zone differences, as some countries may be ahead or behind others in time, so it's important for travelers to take note of these differences to avoid confusion and to make sure they arrive at their destination on time.
It is also important for air and sea transport companies, as they must make sure that their schedules take into account the time difference when crossing the IDL, to avoid confusion and ensure the safety of their passengers.
Overall, the "Date Line" in the travel and transportation context refers to the International Date Line (IDL) which is an imaginary line on the Earth's surface that roughly follows the 180th meridian of longitude, and it is used to determine when a new calendar day begins, and to take into account time zone differences when crossing this line.