UEFA has approved changes to competition regulations for next season, which include a change in Champions League kick-off times and a loosening of restrictions on registering new players.
Games in Europe's top competition, from the play-off round to the final, will now be scheduled to start at 2100CET, rather than the current 2045CET.
However, four group games every week – two on Tuesday, two on Wednesday – will kick off at 1855CET, although all matches will be played simultaneously on matchday six.
Europa League matches will kick off at either 1855CET or 2100CET until the round of 16, after which the later time will be used.
For the Champions League, Europa League and Super Cup finals, a total of 12 substitutes can be named on the bench. UEFA says this will give "clubs and, in particular, coaches more flexibility regarding substitutes, and facilitate their squad management for the most important fixture of the season".
In the knockout rounds as a whole, a fourth substitute will be allowed during extra-time, which will not affect the other three substitutions that can be made.
Meanwhile, a change has been made to the rules regarding the registration of new players for after the group stages. Clubs will now be allowed to register three new eligible players "without any restrictions".
This will avoid situations where January signings are prevented from playing for their new clubs if they have already played in UEFA competition that season, as has happened with Philippe Coutinho at Barcelona and Pierre-Emerick Aubameyang at Arsenal in 2017-18.
The news will be welcomed by Arsenal manager Arsene Wenger, who was critical of the fact record-signing Aubameyang cannot play in the Europa League knockouts because former club Borussia Dortmund dropped into the competition after finishing third in their Champions League group.
"I believe that all the clubs agree now this rule has to disappear in Europe," he said ahead of the last-32 first leg against Ostersunds.
"When you look at the transfer amounts you spend now, that you have to spend 50million, 60million, 70million in the middle of the season, that the players cannot play doesn't make sense."
The changes will be introduced for the Champions League, Europa League and UEFA Super Cup from 2018-19 onwards.