sorry for my ignorance I have no idea about spreadsheets.
What I have is a column that contains dates but they are there in different format some are text like '19.12.2006 and others are cells that are formated as a date like 2009-10-10
I want them all to be date cells, so I found a formula =DATEVALUE
What I done is I put =IF(A2="";"";DATEVALUE(A2))
For the dates in text format it done well, for empty cells it's ok as well, but when the cell is a date cell I have Err: 502
Can anyone please help me?