Nundina › Discover calendars › Firefox Release Schedule calendar › Firefox 166 Merge DayFirefox 166 Merge Day4 February 2027 at 16:00 UTCFirefox 166 Merge Day: code moves from Nightly to Beta (Nightly becomes the next version). Planned for 2027-02-04 16:00 UTC.Firefox Release Schedule calendarMore from this calendar