All abbreviations, or usage of contractions, etc., are due to how the song was originally released.
In the majority of cases, how I listed the song is the official title in accordance to the record label’s printing of the label.
During 2019, so far fourteen singles reached number one on the Hot 100; a fifteenth single, "Thank U, Next" by Ariana Grande, began its run at number one in November 2018.
Of those fourteen number-one singles, four were collaborations.
When you scroll down the list you will see that the first entry of each week of each month begins with the highest charted single of that month and then alphabetical by artists.
The debut of the “Rock Era” is commonly known to be June 1955, when Bill Haley’s “(We’re Gonna) Rock Around The Clock” hit #1 on the Billboard pop/Top 40 charts.
Sometimes the difference between official release date and chart release date can differ, usually by no more than a week or two, but can go as long as years, depending on who released the single, and why it took so long to be released.
Post Malone and Ariana Grande were the only acts to have multiple number one songs in 2019, with two.
Despite being released in 2017, "Truth Hurts" became Lizzo's (pictured) first number-one hit and first Hot 100 chart entry in general.
This is with the exception of any single that only made it under the Hot 100 (commonly known as a “Bubbling Under”).
NOTE: Currently, the website is only updated to 2013.