1. accepts seconds since epoch, ms since epoch, a valid bson ObjectId & any string that PHP’s strtotime function understands as input.
2. tack on json=1 to the URL to get output as json
3. tack on f=local, f=utc or f=unixtime to the URL to get just a single field from the json output

Obviously it would be nice to be able to skip the web browser thing and get at it from the terminal. Simple enough - just add something like this to your .bash_profile

nixtime "string or timestamp to get data for".