Give some stream of consciousness and then the answer. The duties of the White House chief of staff vary greatly from one administration to another and, in fact, there is no legal requirement that the president even fill the position. However, since at least 1979, all presidents have found the need for a chief of staff, who typically oversees the actions of the White House staff, manages the president's schedule, and decides who is allowed to meet with the president. Because of these duties, the chief of staff has at various times been labeled "The Gatekeeper", or "the power behind the throne".

Based on this passage, who takes care of the president's schedule?
The relevant information to answer the above question is: However, since at least 1979, all presidents have found the need for a chief of staff, who typically oversees the actions of the White House staff, manages the president's schedule, and decides who is allowed to meet with the president.
Therefore, the answer is White House chief of staff.