Super League has delayed the start of the 2021 season until 25 March, while Championship and League One clubs have also agreed with the Rugby Football League to push back their campaigns.
With tighter Covid-19 restrictions currently in place, the leagues have all opted to give themselves more time to prepare.
Super League will kick off two weeks later than originally planned.
However, there is no change to the Grand Final 'end' date of 9 October.
Full details on the fixture schedule and structure for 2021 in the top flight will be revealed in due course.
An announcement is expected this weekend about the Championship and League One, along with information about the early rounds of the Challenge Cup.
The second-tier clubs were to start their season in late February, but that will now be moved on "several weeks", while League One clubs have targeted a date "later in the spring" to begin.
Meanwhile, Women's Super League clubs will also learn their timetable this weekend for a proposed pre-season and return-to-play, and the England women's team's plans for a training camp will be put back as well.
Returning to training 'responsibly and constructively'
Players at Championship clubs will be allowed to resume distanced, non-contact training from Saturday, with a view to stepping up to contact next month.
The same staggered approach will also be applied to League One players, when they begin their pre-season preparations in February.
"We have been grateful to our clubs throughout the last 10 months for their responsible and constructive approach to such a challenging period for all, and Wednesday's meeting was another example of that," RFL chief executive Ralph Rimmer said.
"There remains a desire and determination, from the RFL as well as clubs, to get back on the field as soon as is safely possible. However there is also a recognition of the need to be responsible at this time."