This post is older than a year. Consider some information might not be accurate anymore.
A small example how to use the date function in the linux shell. For ISO-Format yyyy-MM-dd ⇒ %Y-%m-%d
pi@dojo:~$ echo $(date +%Y-%m-%d)
2013-01-23
With time
pi@dojo:~$ echo $(date +%Y-%m-%d\ %H:%M:%S)
2013-01-23 21:37:09
