Question: The President whose cabinet James Mattis served on assumed office on what date?

Context paragraphs:
James Mattis: James Norman "Jim" Mattis (born September 8, 1950) is a retired United States Marine Corps general who is the 26th and current United States Secretary of Defense, serving in the Cabinet of Donald Trump.  Mattis was previously the 11th Commander of United States Central Command during the presidency of Barack Obama, and was responsible for American military operations in the Middle East, Northeast Africa, and Central Asia.

Cabinet of Donald Trump: This article lists the members of President Donald Trump's Cabinet.  Trump assumed office on January 20, 2017.

Shadow Cabinet of Thailand: The Shadow Cabinet of Thailand (Thai: คณะรัฐมนตรีเงา or รัฐบาลเงา) is an unofficial group of senior opposition party's spokespeople who form an alternative cabinet to the government.  The shadow cabinet members shadow or mark each individual member of the government.  After the People's Power Party's win in the 2007 general election, the Democrat Party became the sole official opposition party.  Abhisit Vejjajiva, leader of the Democrat Party, expressed his intention to set up a shadow cabinet to track the new administration's performance, to propose better solutions, and to provide the Democrat's standpoint on each government decision.  The shadow cabinet line-up was announced on February 8, 2008 after the Samak's administration had officially assumed office.  On the 15 December 2008, Abhisit was elected by the House of Representatives to become the next Prime Minister, within a week a Cabinet will be formed which will include many members his Shadow Cabinet.  However a day later the For Thais Party (the opposition party) MP Jatuporn Promphan stated that his party will not be forming a Shadow Cabinet.

Duke Records: Duke Records was an American record label, started in Memphis, Tennessee, in 1952 by David James Mattis (WDIA program director and DJ) and Bill Fitzgerald, owners of Tri-State Recording Company.  Their first release was Roscoe Gordon singing "Hey Fat Girl", issued on Duke R-1, later amended to R-101.

Robert Harward: Robert Stiles Harward, Jr. (born 1956/1957), known as Bob Harward, is a retired United States Navy SEAL and a former Deputy Commander of the United States Central Command, under the leadership command of General James Mattis.  He is currently a defense industry executive working for Lockheed Martin.  He also served as the Deputy Commander of U.S. Joint Forces Command and previously commanded Combined Joint Interagency Task Force 435.

Stone v. Trump: Stone v. Trump (1:17-cv-02459-MJG) is a lawsuit filed on August 28, 2017 in the United States District Court for the District of Maryland.  The lawsuit alleges that President Donald Trump's ban on transgender personnel joining the U.S. military violates their equal protection and due process rights.  The American Civil Liberties Union (ACLU) of Maryland filed the suit on behalf of Petty Officer First Class Brock Stone, an 11-year veteran of the U.S. Navy, and several other transgender service members.  In addition to President Trump, the suit names as defendants the Secretaries of Defense (James Mattis), the Army (Ryan McCarthy, acting), the Navy (Richard Spencer), and the Air Force (Heather Wilson).

List of U.S. Department of Defense agencies: This is a list of Agencies under the United States Department of Defense (DoD) which was formerly and shortly known as the National Military Establishment.  Its main responsibilities are to control the Armed Forces of the United States.  The Department was established in 1947 and is currently divided into three major Departments—the Department of the Army, Navy and Air Force—and has a military staff of 1,418,542 (553,044 US Army; 329,304 US Navy; 202,786 US Marine Corps; 333,408 US Air Force).  The DoD is headed by the Secretary of Defense.  The current defense secretary is James Mattis.

Vayl Oxford: Vayl S. Oxford is a national security policy adviser who has been selected by Secretary James Mattis to head the Defense Threat Reduction Agency.  Oxford was previously a security adviser at the Pacific Northwest National Laboratory.

Jill Kelley: Jill Kelley (born June 3, 1975) is a philanthropist, an American socialite, a former South Korean Honorary Consul and the first honorary Ambassador to General James Mattis at United States Central Command, whose reporting of threatening e-mails that she and other top U.S. Generals received by a cyberstalker, Paula Broadwell, led to the David Petraeus scandal.  She has since then become a privacy rights advocate and activist for internet security in her memoir "Collateral Damage: Petraeus, Power, Politics and the Abuse of Privacy" telling her story to "bring awareness to the damages that can be caused by government overreach and unwarranted searches of emails so that history will not repeat itself, and this never happens to another innocent family again."

Ralph Mattis: Ralph Mattis (August 24, 1890 – September 13, 1960), known also as Matty Mattis, was a professional baseball outfielder whose career spanned seven seasons, one of which was spent in Major League Baseball (MLB) with the Pittsburgh Rebels (1914).  In his only season in the majors, Mattis batted .247 with 14 runs scored, 21 hits, four doubles, one triple, and eight runs batted in (RBIs) in 36 games played.  The majority of his career was played in the minor leagues.  He played with the Richmond Colts (1911), Newport News Shipbuilders (1912), Roanoke Tigers (1913), Parksley Spuds (1923–24), and Crisfield Crabbers (1925) over his career in the minors.  Combined between those teams, Mattis batted .303 with 698 hits in 610 games played.  During his career, he stood at 5 ft and weighed 172 lb .  He batted and threw right-handed.  Mattis served as a manager for one season with the Parksley Spuds (1923).

Supporting paragraphs: James Mattis Cabinet of Donald Trump
Answer: January 20, 2017