get date and save it as a file name python

Your filename 05/12/2013.png contains slashes (/) and these are likely pathname separator characters on your OS. In other words, the filename you are trying to write to is 2013.png in the directory 12, under the directory 05. If that's not what you want, then consider changing your filename format to something like time.strftime("%Y-%m-%d"), or anything else without slashes.