This serves up public/private keys for particular moments in time. For moments in the past it reveals both keys. For moments in the future it reveals only the public key.
You can use this to assure that something is impossible prior to it's proper time. For examples:
Currently we only do dates, for example http://hang-on.appspot.com/k/2009/12/25, or http://hang-on.appspot.com/k/2009/10/31. Use four digit years, and two digits for the month and days.
This is a demo, no promises!