Nundina › Discover calendars › Firefox Release Schedule calendar › Firefox 158 Merge DayFirefox 158 Merge Day27 September 2026 at 00:00 UTCFirefox 158 Merge Day: code moves from Nightly to Beta (Nightly becomes the next version). Planned for 2026-09-27 00:00 UTC.Firefox Release Schedule calendarMore from this calendar