Yeah... that can work and I will more than likely use that for the time being...
BUT
I have to do it for each 'campaign'... I actually have a lot more to send than my current limit will allow so I keep 'duplicating' my campaign and I would need to remember to update that... and I send the same email at different times of the year as reminders to quite a large group ...
SO
the datestamp / time would help to track when people are doing what they are supposed to do... without me remembering that...
That sounds like you could use the new Autoresponders.
Create a date based custom field, then create a date based autoresponder to send emails to each individual subscriber when the date arrives or nears (you can set this down to the minute).