The Billboard Hot 100 is the United States music industry standard singles popularity chart issued weekly by Billboard magazine. Chart rankings are based on radio play and sales; the tracking-week for sales begins on Monday and ends on Sunday, while the radio play tracking-week runs from Wednesday to Tuesday. A new chart is compiled and officially released to the public by Billboard on Thursday. Each chart is dated with the "week-ending" date of the Saturday two weeks after. Example:
- Monday, January 1 – sales tracking-week begins
- Wednesday, January 3 – airplay tracking-week begins
- Sunday, January 7 – sales tracking-week ends
- Tuesday, January 9 – airplay tracking-week ends
- Thursday, January 11 – new chart released, with issue date of Saturday, January 20.
The first number one song of the Hot 100 was "Poor Little Fool" by Ricky Nelson on August 4, 1958.