Wiser Monks Than I_(TM) can provide specific answers to your question.
But a Super Search for unique filename timestamp date turned up some hopefully helpful threads:

• How do I make a temporary file name?
• Date extraction
• Creating files
• How can I reliably rename a file?
• converting timestamps

I vaguely recall a question just like yours sometime in the past few months, but haven't found it.

Good luck, and let us know how you end up handling this.
    cheers,
    ybiC