Is that the empty String? It cannot be turned into a number You didn't say where that is happening, but you might be getting text from a text component which hasn't been filled in yet. It shows you that users can be relied upon to find a way to pass wrong input ; you will have to find a way to stop them.
what i am trying to do is i want to give user an ooption to chose date and month from the drop down list which came from database and also day too. once the chose the month,year and day then i want to get that value and combine all and convert into a date..but for some reason when i am chosing year and month its not taking. where did i do wrong?