Both of those competitions have observed format variations, with expansions in the number of collaborating teams, introduction of new rounds, and changes in qualification conditions over the years. The group stage was played from September to December, whilst the knockout stage started in February, with matches normally played on Tuesday https://louisiapao.blogoscience.com/42837616/getting-my-what-are-the-uefa-champions-league-and-uefa-europa-league-to-work