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Firstly, to bring order to the global registration system, world governing body Fifa only permits the transfer window in any individual country to be open for 16 weeks in any calendar year.

In Europe, precedent dictates four of those weeks are for the winter window, leaving 12 in the summer. In 2024, the Premier League transfer window opened on 14 June and closed on 30 August.

However, in October, Fifa approved an additional window from 1-10 June that would allow the 32 clubs competing in the Club World Cup to register new players before the tournament.

It also agreed to open a registration window mid-tournament, from 27 June and 3 July, to allow clubs to register additional players for the knockout stage.

As well as Manchester City and Chelsea, European heavyweights Real Madrid, Atletico Madrid, Inter Milan, Juventus, Paris St-Germain, Bayern Munich, Borussia Dortmund and Saudi Arabia’s Al-Hilal are among others playing in the tournament.

In order to ensure Manchester City and Chelsea did not have an advantage over the other 18 top-flight clubs, the Premier League has adopted the same window.

However, 12 weeks from 1 June is 24 August. The Premier League wanted to be aligned with the rest of Europe’s big leagues around when the summer window closes. Those leagues preferred to close the window at the end of August, so that meant the window had to close and reopen.