It should be on the label as either "PHI" or the words "pre-harvest interval" which is the number of days or weeks you must wait.

Daconil has no pre-harvest interval for tomatoes; this information sheet from University of Wisconsin lists the pre-harvest interval for all products containing chlorothalonil as 0 days when applied to tomatoes. It's fairly inert and doesn't get into plant tissues at all; it just acts as a physical barrier against fungal penetration.

If it eases your mind at all, the toxicity of chlorothalonil is really, really low in mammals, lower than many organic treatments like sulfur; even if you eat a little by accident, it won't hurt you. So just wash the fruit before you eat them, and follow any other label directions.

--Alison