Sandford Fleming, Scottish-Canadian engineer, created Universal Standard Time (died 1915)

Sir Sandford Fleming was a Scottish Canadian engineer and inventor. Born and raised in Scotland, he immigrated to colonial Canada at the age of 18. He promoted worldwide standard time zones, a prime meridian, and use of the 24-hour clock as key elements to communicating the accurate time, all of which influenced the creation of Coordinated Universal Time. He designed Canada's first postage stamp, produced a great deal of work in the fields of land surveying and map making, engineered much of the Intercolonial Railway and the first several hundred kilometers of the Canadian Pacific Railway, and was a founding member of the Royal Society of Canada and founder of the Canadian Institute.

Universal Time is a time standard based on Earth's rotation. While originally it was mean solar time at 0° longitude, precise measurements of the Sun are difficult. Therefore, UT1 is computed from a measure of the Earth's angle with respect to the International Celestial Reference Frame (ICRF), called the Earth Rotation Angle. UT1 is the same everywhere on Earth. UT1 is required to follow the relationship