Hello Terumasa,
There has been a lot going on with VDE-0884-10 in the last few months of 2014. Originally that date actually was when the standard expired. So the certification would expire at the same time.
Late in 2014 VDE approved VDE-0884-10 Ed.2, an update to the standard, which adds three years of applicability to the current version of the standard and the certifications that it generates. At the end of that time period, these certificates should be replace with ED. 2 certificates. The latest version removes that text. The wrinkle here is that we are rolling out a new version of the web site very soon and they do not want big changes in content just as they are changing over so the latest version is in my hands, but not on the web. I will send you a copy.
I hope this clear it up for you,
Best regards,
MSCasntrell