The "Value" can either be a date in the format: CCYY-MM-DD HH:MM:SS or the word "now" to use the current time. You may enter a positive or negative number in the "Option" field that will represent the amount of seconds that will be added or substracted to the time; this is most useful when combined with "now". If you have the jscalendar module from jstools installed, you can use a popup date picker here.