Hello, when I convert a factor like this a=01.10.2009 into a date using b=strptime(a, format="%d. %m. %Y"). It works very well. But when I try to convert c = 2009/10 into a date using d=strptime(c, format="%Y/%m") it doesnt work at all. I get d=NA. What did I do wrong? Thank you very much for your help! best regards Claudia