text: The Tonight Show became the first American television program to broadcast with MTS stereo sound in 1984, at first sporadically, by audio engineer Ron Estes. Regular use of MTS began in 1985. In September 1991, the show's start time was shifted by five minutes to 11:35, in order to give network affiliates the opportunity to sell additional advertising during their late local newscasts. On April 26, 1999, the show started broadcasting in 1080i HDTV, becoming the first American nightly talk show to be shot in that format.
  On March 19, 2009, The Tonight Show became the first late-night talk show in history to have the sitting President of the United States as a guest, when President Barack Obama visited Jay Leno.
  Throughout the years, the starting time and the length of The Tonight Show has changed multiple times.
  First run episodes
  §Many NBC affiliates chose not to carry the first fifteen minutes of the show during this period, instead preferring to air a local newscast from 11 p.m. to 11:30 p.m. As of February 1965, Carson refused to host the first 15 minutes of the program, preferring to wait until the full network was in place before delivering his opening monologue; Ed McMahon hosted the program's first 15 minutes instead. This persisted for nearly two years, until the show's start time was finally adjusted to 11:30 p.m. in January 1967.
  Weekend repeats
  From 1965 to 1975, until the premiere of Saturday Night Live, weekend repeats of The Tonight Show were staples of the NBC schedule. These repeats ran in the following time slots:
  Gags, sketches, and segments