The "Office 365 Roadmap Watch" site is developed and maintained by Joe Palarchio; the site is no way affiliated with Microsoft. The "official" Office 365 Roadmap site should be considered the authoritative source for feature changes related to Office 365. The intent of this site is to make it easier to see the feature changes over a period of time for those interested in watching the changes.
The data on this site goes back to March 30, 2015. If you see a feature that was added on that date, it's likely that it was added into the database at that time but was added to the roadmap earlier.
Contact me via Twitter: @JoePalarchio