Make sure you have the timezone set correctly for each feed. On the "feeds" tab you can click "edit" and then look for the timezone. This will help ensure the time you are seeing is what you have in mind.
With the volume of mailings we send out, the feed really only *starts* to be sent at the time you set - meaning it enters our queue along with other mailings. It could take several hours (or longer) to go out, especially if you have a large number of recipients. Also, keep in mind that subscribers receive the mailing across a period of time - not all at once - so the time you receive it may be slightly different (+/- an hour or two) than your other subscribers.
If your mailings consistently go out an hour or so after you were expecting, you can try setting the send time to an hour earlier when editing your feed.