Problem localize birthday

I have read all the issues about localize. We understand now that localize had to be NO on a field like Birthday.But it wasn't. Now we have several problems with this field: export to pdf shows birthday minus 1, etc. How to fix this? It concerns about 1000 employee's. I of course can change this field to NO but that will only have effect for new entry's in the database..... A few examples: "1979-09-20 23:00:00" "1969-04-23 22:00:00" "1990-04-10 22:00:00" "1965-01-07 22:00:00" "1981-03-13 23:00:00" "1961-12-15 23:00:00"
1 answers

You'l have to manually change the data, using an SQL script or writing a microflow that does this for you. It might not always be easy 'cause how the date ended up in the database will depend on in which timezone and daylight savings period it was entered. You can usually make an educated guess though. Luckily it aren't that many records.