As a general rule of thumb cut-off times are 4 hours before close of business to get APPROVAL on a campaign in order to guarantee delivery for the NEXT business day.
This can and will vary on certain busy days of the year prior to holidays such as Thanksgiving, Black Friday, Cyber Monday, etc...
Any approvals made outside of this time frame will be handled on opening of next business day unless otherwise notified (clients must contact their sales representative).