Product Details is a public JSON API which contains release information for Firefox desktop, Fenix and Thunderbird. The data contains release dates for different product versions.
Product Details data is exported to BigQuery daily. Data for Firefox Desktop releases is available at
mozdata.telemetry.releases and for Fenix releases at
As an example, the following query finds release dates for each non-dev release in the Firefox 82 series:
SELECT date, version FROM mozdata.telemetry.releases WHERE version LIKE "82.%" AND category != "dev" ORDER BY date