Final answer:
The International Date Line is a proper noun and should always be capitalized. It is a specific term that refers to an imaginary line on Earth demarcating the change in calendar days.
Step-by-step explanation:
Yes, the term 'International Date Line' is indeed a proper noun and should always be capitalized. A proper noun is a specific name for a particular person, place, or thing, and in English, they are always capitalized. The International Date Line is a unique name that has been set by international agreement to represent an imaginary line on Earth that demarcates the change of one calendar day to the next. This line runs approximately along the 180° meridian of longitude, in the middle of the Pacific Ocean. The specific designation of this line and its purpose in our global timekeeping system make it a proper noun.
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