French FA president Noel Le Graet has revealed UEFA will unveil their plan for next season on June 18.
Rangers are awaiting confirmation as to when the second leg of their Europa League last 16 clash with Bayer Leverkusen can go ahead.
It's been claimed that will be scheduled for August 6 - the same week as the Scottish Premiership has been pencilled in to start the 2020/21 campaign.
But European football's governing body has yet to confirm those dates or the European and international dates for next season too, after postponing their Executive Committee's meeting originally scheduled for the end of last month.
French football chief Le Graet has revealed that UEFA have so many items to discuss on their agenda, the packed June 17 meeting has now been extended to two days.
And national leagues and associations will have to wait until then to announce next season's calendar.
Le Graet said: "UEFA will now take two days to get through this meeting.
"I believe all the international calendars, the league fixture rounds and the dates of the Champions League and Europa League will be official on the afternoon of June 18.
"Each national association and league can then publish their calendars after that.
"We have already prepared ours, but there is nothing we can do officially until UEFA confirm the dates and that's the same with every country in Europe."
UEFA also have to confirm the host cities and rescheduled dates for the postponed Euro 2020 tournament as well as new dates for all sections of international football.
Scotland will also discover when their delayed Euros semi-final play-off with Israel will take place, as well as their Nations League campaign.
