Some all-Welsh games are set to be played midweek because of the Irish and Scottish desire to avoid clashes with international weekends.
Ospreys' stadium share with Swansea City FC caused further trouble, meaning the revision of a fixture with Munster.
More Irish games are set to be played on Friday for the sake of Setanta TV, although some will remain on Sundays.
"We're pretty close to a fixture list, we're within one or two games and then we have to talk to the broadcasters," Celtic League chairman John Hussey told BBC Sport Wales after a meeting in Dublin.