Question: When were the Billboard Charts for music begin?

Billboard charts

''Billboard'' charts
The Billboard charts tabulate the relative weekly popularity of songs and albums in the United States and elsewhere.  The results are published in Billboard magazine. Billboard biz, the online extension of the Billboard charts, provides additional weekly charts.[1] There are also Year End charts.[2]  The charts may be dedicated to specific genre such as R&B, country or rock, or they may cover all genres. The charts can be ranked according to sales, streams or airplay, and for main song charts such as the Hot 100 song chart, all three pools of data are used to compile the charts.[3]  For the Billboard 200 album chart, streams and track sales are included in addition to album sales.[4]
The weekly sales and streams charts are monitored on a Friday-to-Thursday cycle since July 2015, previously it was on a Monday-to-Sunday cycle.  Radio airplay song charts however follows the Monday to Sunday cycle (previously Wednesday to Tuesday).[5] The charts are released each Tuesday with an issue date the following Saturday, four days later.
History, methods and description

On January 4, 1936, Billboard magazine published its first music hit parade.[6] The first Music Popularity Chart was calculated in July 1940.  A variety of song charts followed, which were eventually consolidated into the Hot 100 by mid-1958.  The Hot 100 currently combines single sales, radio airplay, digital downloads, and streaming activity (including data from YouTube and other video sites). All of the Billboard charts use this basic formula. What separates the charts is which stations and stores are used; each musical genre has a core audience or retail group. Each genre's department at Billboard is headed up by a chart manager, who makes these determinations.
For many years, a song had to be commercially available as a single to be considered for any of the Billboard charts. At the time, instead of using Nielsen SoundScan or Nielsen Broadcast Data Systems (BDS), Billboard obtained its data from manual reports filled out by radio stations and stores. According to the 50th Anniversary issue of Billboard, prior to the official implementation of SoundScan tracking in November 1991, many radio stations and retail stores removed songs from their manual reports after the associated record labels stopped promoting a particular single. Thus songs fell quickly after peaking and had shorter chart lives.  In 1990, the country singles chart was the first chart to use SoundScan and BDS. They were followed by the Hot 100 and the R&B chart in 1991. Today, all of the Billboard charts use this technology.
Originally, Billboard had separate charts for different measures of popularity, including disc jockey playings, juke box song selection, and best selling records in retail stores. A composite standing chart that combined these gradually grew to become a top 100, the predecessor to the current Hot 100 chart. The juke box chart ceased publication after the June 17, 1957 issue, the disk jockey chart, after the July 28, 1958 issue, and the best seller chart, after the October 13, 1958 issue. The July 28, 1958 issue was also the last issue that called the composite chart the "Top 100"; the following week began the "Hot 100". Billboard publishes many different charts, with the Hot 100 and Billboard 200 being the most famous. Billboard also has charts for the following music styles: rock, country, dance, bluegrass, jazz, classical, R&B, rap, electronic, pop, Latin, Christian music, comedy albums, catalog albums, and even ringtones for mobile (cell) phones. In 2009 Billboard partnered with MetroLyrics to offer top 10 lyrics for each of the charts.
At the end of each year, Billboard tallies the results of all of its charts, and the results are published in a year-end issue and heard on year-end editions of its American Top 40 and American Country Countdown radio broadcasts. Between 1991 and 2006, the top single/album/artist(s) in each of those charts was/were awarded in the form of the annual Billboard Music Awards, which were held in December until the awards went dormant in 2007. The awards returned in May 2011.
Before September 1995, singles were allowed to chart in the week they first went on sale based on airplay points alone. The policy was changed in September 1995, to only allow a single to debut after a full week of sales on combined sales and airplay points. This allowed several tracks to debut at number one.
In December 1998, the policy was further modified to allow tracks to chart on the basis of airplay alone without a commercial release.  This change was made to reflect the changing realities of the music business. Previous to this, several substantial radio and MTV hits had not appeared on the Billboard chart at all, because many major labels chose not to release them as standalone singles, hoping their unavailability would spur greater album sales. Not offering a popular song to the public as a single was unheard of before the 1970s. The genres that suffered most at the time were those that increasingly impacted pop culture, including new genres such as trip hop and grunge. Among the many pre-1999 songs that had ended up in this Hot 100 limbo were The Cardigans' "Lovefool", Natalie Imbruglia's "Torn" (which peaked at forty-two), Goo Goo Dolls' "Iris" (which hit #9), OMC's "How Bizarre", Sugar Ray's "Fly" and No Doubt's "Don't Speak".
On June 25, 2015, Billboard made changes in its chart requirements. The official street date for all new album releases was moved from Tuesday to Friday in the United States.  For all sales-based charts (ranking both albums and tracks), Billboard and Nielsen changed the chart reporting period to cover the first seven days of an album's release. As a result of the changes, The Billboard 200, Top Albums Sales, Genre-based albums, Digital Songs, genre-based downloads, Streaming Songs, and genre-focused streaming surveys ran on a Friday to Thursday cycle.  Radio Songs, which informs the Hot 100, synched to the Monday to Sunday period after formerly covering Wednesday to Tuesday. All other radio charts and genre tallies followed the Monday to Sunday cycle. The move was made to coincide with the IFPI's move to have all singles and albums released globally on Fridays.[5]
Incorporating digital platforms
Starting in 2005, Billboard changed its methodology to include paid digital downloads from digital music retailers such as Rhapsody, AmazonMP3 and iTunes. This change also allowed songs to chart with or without the help of radio airplay. This meant that a song did not need radio airplay to be eligible to chart on the Billboard Hot 100. With this policy change, a song could chart based on digital downloads alone.[7]
On July 31, 2007, Billboard changed its methodology for the Hot 100 chart to include digital streams. The digital information at the time was obtained from Yahoo and AOL's streaming platforms. This change was made exclusively to the Billboard Hot 100 Chart. The effect of this chart change was minuscule at the time because it was estimated to account for 5% of the chart's total points.[8]
In October 2012, Billboard dramatically changed the methodology for their country, rock, Latin, and rap charts, when they incorporated sales of digital downloads and streaming plays into what had been airplay-only charts. Another change was that rather than measuring airplay only from radio stations of the particular genre, the new methodology measures airplay from all radio formats.[9] This methodology was extended to their Christian and gospel charts in late 2013.[10] These methodology changes resulted in higher positions on the genre charts for songs with crossover appeal to other genres and radio formats (especially pop) at the expense of songs that appeal almost exclusively to core fans of the given genre, which was controversial with those devotees.[11]
On February 20, 2013, Billboard announced another change in the methodology for their charts that incorporated YouTube video streaming data into the determination of ranking positions on their streaming charts. The incorporation of YouTube streaming data enhanced a formula that includes on-demand audio streaming and online radio streaming. The YouTube video streams that used in this methodology are official video streams, Vevo on YouTube streams, and user-generated clips that utilize authorized audio. Billboard argued that this change was made to further reflect the divergent platforms of music consumption in today's world.[12]
Singles and tracks
All-genre

R&B/Hip-Hop

Adult/Pop

Country

Rock

Dance

Latin

Christian

Jazz

Holiday

Ringtones

Spotify

Canadian charts

International charts

Discontinued charts

Notes

Albums

Video

Other charts
In December 2010, Billboard announced a new chart titled Social 50, which ranks the most active artists on the world's leading social networking sites. The Social 50 chart tallies artists' popularity using their weekly additions of friends/fans/followers, along with weekly artist page views and weekly song plays on Myspace, YouTube, Facebook, Twitter and iLike.[29]
In January 2011, Billboard introduced another chart called Uncharted, which lists new and developing artists, who are yet to appear on any major Billboard chart, "...regardless of their country of origin."[30] The ranking is based on the views and fans on social networking websites like Myspace and Facebook. To appear on Uncharted, the artists must be registered Myspace Music artists, and should not have appeared on any major Billboard charts before.[30]
In May 2014, after the Korea K-Pop Hot 100 chart was discontinued in the U.S., the Billboard K-Town column continued to provide chart information for K-pop artists on all Billboard charts.[20][22]
The Billboard Artist 100 began in 2014.
Further reading
Durkee, Rob. "American Top 40: The Countdown of the Century." Schriner Books, New York City, 1999.
Battistini, Pete. "American Top 40 with Casey Kasem The 1970s." Authorhouse.com, January 31, 2005.  ISBN1-4184-1070-5