Borders in Europe are fluid.
There are big changes, such as the (disputed) creation of the new country of Kosovo a decade or so ago. In the second half of the 20th century, Yugoslavia split up, as did Czechoslovakia and the Soviet Union. There were many more changes in the first half of that century, following two world wars. The losers lost territory, the victors gained.
Then you have the small changes, where countries willingly swap territory, often for mundane reasons. For example, Luxembourg and France swapped a few acres a decade ago to make it easier for a motorway exit to be built in Luxembourg (just down the road from me). Belgium and the Netherlands swapped some fields recently to aid policing.
European borders are always changing.
Originally posted on quora.