Multiple independent sources state that Callin’s public launch occurred on September 2, 2021. David Sacks’ own launch blog post on Medium, dated September 2, 2021, explicitly says “Today is the public launch of Callin,” confirming that this was the day the app became publicly available on the Apple App Store. (medium.com) TechCrunch’s coverage likewise reports that Callin “launches” on September 2, 2021, alongside its $12M Series A announcement. (techcrunch.com) Forbes also runs a feature on the same date describing Sacks as “launching the ‘social podcasting’ platform Callin on the Apple App Store.” (forbes.com) Additional funding and news databases (Crunchbase, VC News Daily) list the product launch and funding announcement on September 2, 2021. (crunchbase.com) Together, these sources confirm that the Callin app’s public launch did indeed occur on 2021-09-02, matching the prediction.