At 11 p.m. this evening, Friday, 31 January 2020, the UK leaves the European Union. It is no longer a member in law. The necessary legislation has gone through both the UK Parliament and the EU Parliament. It is all change.
But for family law, and indeed for much else, it is in fact no change until the end of the year on 31 December 2020. This is the implementation period, previously referred to as the transition period.