German Bundesliga clubs have a habit of wrapping up transfer deals even before the official start of a transfer window, which is by no mean a bad thing, seeing that this helps the teams prepare for the new season in the best possible way.
While the summer transfer window is open from 1 July to 31 August, winter transfer window lasts from 1 January to 31 January, but it is important to note that the deadline in Germany is at 18:00, some 6 hours before the transfer window closes in most other leagues. FIFA Transfer Matching System ensures that only deals confirmed by both selling and buying club are processed, thus making sure there are no last minute hiccups.