I researched this because I was genuinely curious. It seem that....
1985 - 1992: The NFL started the weekend after Labor Day and finished the final Sunday in January (except in 1989 where they started Labor Day weekend and finished the 2nd to last Sunday in January). 16 games, no bye except a bye before the Super Bowl
1993: The NFL gave every team 2 byes but took away the Super Bowl bye. This moved the start up one weekend to Labor Day, and still finished the final Sunday in January
1994 - 1998; 2000: They changed it to 1 bye per team, and resumed the Super Bowl bye, so it was still starting on Labor Day weekend and ending the final Sunday in January. In 1997, the opening Sunday was actually on August 31.
1999, 2001, 2002: They started the week after Labor Day and took away the Super Bowl bye to finish the final Sunday in January. As we all know, the September 11 cancellations pushed the playoffs back a week that year. Because of this, February 3, 2002, was the first February Super Bowl even though it was not planned that way. A dynasty was born.
2003 - 2020: Start the week after Labor Day, finish the first Sunday in February.
2021 - ????: If Peter King is right, start the week after Labor Day, finish the second Sunday in Feburary. This, of course, will lead to Armageddon and a complete breakdown of societal law and order in 2027 when the Super Bowl falls on Valentine's Day.