It depends. Most of our data traces back to August of 2016. Considering Chartmetric didn't launch until November 2016 we think that's pretty cool.
Here is an up to date list with more detailed breakdowns of how much data we have.
Here is the earliest date for the data we have, for each platform:
Social Media:
Facebook: April 20th, 2016
Instagram: March 23rd, 2016
Wikipedia: April 4th, 2016
Twitter: March 23rd, 2016
Soundcloud: April 27th, 2017
Youtube Channel: March 23rd, 2016
YouTube For Artists: August 22nd, 2017
Deezer: May 2nd, 2017
Bandsintown: January 12th, 2017
Genius: August 16th, 2018
Streaming service and Playlists:
Spotify artist: November 25th, 2016
Spotify playlist: November 4th, 2016
Apple Music: April 20th, 2018
Deezer: February 15th, 2018
Amazon Music: January 25th, 2019
Charts:
Spotify: April 14th, 2016
Apple Music: July 17th, 2017
Amazon Music: January 25th, 2019
Deezer: March 1st, 2019
iTunes: April 1st, 2017
Shazam: April 10th, 2017
YouTube: September 21, 2017`
Beatport: June 27th, 2017
Soundcloud: December 7th, 2018
QQ Music: January 11th, 2018
Misc:
TVMaze: January 3rd, 2005
Tunefind: May 18th, 2016
Radiowave: September 25th, 2018
Songkick: January 1st, 2010
Chartmetric Artist Score and Rank: June 10, 2019