Regarding the registration of players after a group stage of the UEFA Champions League and UEFA Europa League, *a club may register three new eligible players without any restrictions*. This is in line with the existing regulatory situation in the different domestic leagues, which does not impose restrictions on the eligibility for competitions of players registered for a new club during the winter transfer window.
Exceptionally for the UEFA Champions League *FINAL*, UEFA Europa League *final* and UEFA Super Cup, 23 players (instead of 18 players for all other matches) may be included on the match sheet. This will allow 12 substitutes (instead of seven) to sit on the bench in these finals – giving clubs and, in particular, coaches more flexibility regarding substitutes, and facilitate their squad management for the most important fixture of the season.
The extra players are only allowed in those three finals – not the regular UCL games.
The quote from UEFA is:
New kick-off times in the UEFA Champions League and UEFA Europa League:
UEFA Champions League play-offs, group-stage games, round of 16 matches, quarter-finals, semi-finals and the final *will kick off at 21:00CET*. However, on every group-stage matchday, *two of the Tuesday and two of the Wednesday matches will kick off at 18:55CET*.
All fixtures on the *last matchday will be played simultaneously*.
UEFA Europa League matches from the group stage until round of 16 matches will kick off at 18:55 and 21:00CET. The kick-off times will be decided in accordance with the draw. In principle, games within a group will be played simultaneously on the last matchday. The quarter-finals, semi-finals and final will all kick off at 21:00CET.
• From the 2018/19 season, a fourth substitute listed on the match sheet may take part in knockout matches exclusively during extra time. This will not affect the other three substitutions.
UEFA CHAMPIONS LEAGUE CALENDAR FROM AUGUST 2018 – JUNE 2019
1 August: Second qualifying round, second leg
6 August: Play-off round draw, Nyon
7/8 August: Third qualifying round, first leg
14 August: Third qualifying round, second leg
21/22 August: Play-off round, first leg
28/29 August: Play-off round, second leg
30th August: Group stage draw, Monaco
18/19 September: Group stage, matchday one
2/3 October: Group stage, matchday two
23/24 October: Group stage, matchday three
6/7 November: Group stage, matchday four
27/28 November: Group stage, matchday five
11/12 December: Group stage, matchday six
17 December: Round of 16 Draw, Nyon
12/13/19/20 February: Round of 16, first leg
5/6/12/13 March: Round of 16, second leg
15 March: Quarter-final and semi-final draws, Nyon
9/10 April: Quarter-finals, first leg
16/17 April: Quarter-finals, second leg
30 April: Semi-finals, first leg
1 May: Semi-finals, first leg
7/8 May: Semi-finals, second leg
1 June: Final – Estadio Metropolitano, Madrid
All dates are provisional and subject to change by UEFA_