The 24-hour clock is a convention of time keeping in which the day runs from midnight to midnight and is divided into 24 hours, indicated by the hours passed since midnight, from 0 to 23. This system is the most commonly used time notation in the world today. It is the international standard notation of time (ISO 8601). In the practice of medicine, the 24-hour clock is generally used in documentation of care as it prevents any ambiguity as to when events occurred in a patient's medical history. It is popularly referred to as military time or astronomical time in the United States and Canada, where the 12-hour clock is still dominant (in addition to a handful of other countries).

Thomas James "Tom" Vilsack (/ˈvɪlsæk/; born December 13, 1950) is an American politician, a member of the Democratic Party, and presently the U.S. Secretary of Agriculture. He served as the 40th Governor of the state of Iowa. He was first elected in 1998 and re-elected to a second four-year term in 2002. On November 30, 2006, he formally launched his candidacy for the Democratic Party's nomination for President of the United States in the 2008 election, but ended his bid on February 23, 2007.

Barack Obama announced Vilsack's selection to be the United States Secretary of Agriculture under his administration on December 17, 2008. Vilsack's nomination was confirmed by the United States Senate by unanimous consent on January 20, 2009.

Born in Pittsburgh, Pennsylvania, Tom Vilsack was abandoned at birth and placed in a Roman Catholic orphanage. He was adopted in 1951 by Bud and Dolly Vilsack, who raised him in the Roman Catholic faith. His adoptive father was a real-estate agent and insurance salesman, and his adoptive mother was a homemaker.