Football transfer market in Europe differ from one country to another, but most start on 1st of January and 1st of July, while closing on 31st of January and 31st of August.
Transfer Window is the unofficial term commonly used by the media for the concept of “registration period”, as described in the FIFA Regulations on their Status and Transfer of Player, and refers to a period during the year in which a football club can transfer players from other countries into their playing staff, without prejudice of their right to sign additional players outside the said periods, eg. If all its goalkeepers are injured.
Although, FIFA´s transfer rules are a derogation from normal employment practices, all European leagues observe them and have players moved within the established periods. There is some flexibility and subtle differences in the way transfers are processed because the exact regulations and possible exceptions are established by each competition´s governing body rather than by the national football association.
In the case of the English Premier League, the deadline for the summer window can be extended for a day or two, to the following Monday. Also, after FIFA decided to scrap the Emergency Loan Window, all loan deals now must be completed before said deadlines, although free agents can move outside the windows.
The English Premier League transfers section not only cover the purchases but also free transfers and loan deals, displaying the player involved, his nationality and position, his old and new club, as well as the price of the transfer, when available. Premiership clubs often decide not to reveal the agreed transfer fee, so these kind of deals are regarded as “undisclosed” until transfer fee has officially been announced by reliable sources.
German Bundesliga clubs usually wrap up transfer deals even before the official start of a transfer window, which is by no mean bad a thing, seeing that this helps the teams prepare for the new season in the best possible way. While transfers are usually processed during standard windows, the deadline in Germany is at 18:00, some 6 hours before most other leagues.
The Spanish La Liga, like other top leagues, only allows clubs to sign new players during standard transfer windows. However, free transfers players (without a contract with another team) can be completed outside said dates.
La Liga transfer`s page only contains officially confirmed deals or free transfers, meaning that all arrangements appearing here are done and dusted. On the other hand, transfer rumours deals expected to be completed soon can be found on other of their pages.
All transfers on above and other European leagues are processed using the FIFA Transfer Matching System (ITMS) that requires both, the selling and buying club to submit full details of the deal. The transfer is only ratified and confirmed if the details submitted by both clubs match, thus making sure there are no last minute hiccups.