It looks like WebDirect is applying US date formats on a UK formatted file. This file was created on a computer running UK date formats and has been working properly for several years. We've enabled WebDirect for some aspects of it's functionality but we've found that it's treating dates incorrectly.
FileMaker Server 126.96.36.1992
Windows Server 2012 Standard Build 9200
Both Chrome Version 51.0.2704.84 (64-bit) and Safari 9.03 exhibit this behaviour on OS X 10.10.5
Problem is illustrated in the following screenshot:
FileMaker Pro Advanced 15.01 on the left and WebDirect on the right. They're both looking at the same field on the same record but the WebDirect date picker appears to think the date is in US format. This file has never been on a computer running US date formats. The yellow text is showing the result of inserting a date placeholder on the layout.