The holiday has always been on the first Monday of the month since its inception 16 years ago. But in 1995, it will fall a week later, on 8 May, to coincide with celebrations for the 50th anniversary of VE Day.
The change was announced in a low- profile parliamentary written answer just before Christmas. Publishers were reported to have printed millions of diaries and calendars with the wrong date.
'Clearly, it is to be regretted . . . but we did not get around to announcing it,' said a spokeswoman for the Department of Employment, where the buck stops in this case.
Letts' operations director, Keith Taylor, said the firm only used the latest information. All editions of Letts 1995 diaries he had checked had the correct date.