The record covers six sites, one of which - Maastricht - celebrated four years without a lost time accident just one month later.
"We are all very pleased with what we have achieved here," said operations director Laurens Aveskamp."We began a serious campaign to improve our safety performance about six years ago and have steadily reduced the number of accidents and incidents year by year.
We passed the year mark on April 21 and then soon afterwards, Maastricht's excellent achievement gave us a double celebration."