Comparison date fields shouldn't include time

I have a custom workflow to determine projects that went late under certain criteria.  My current rule includes $C_AuthorizedEndDate <$C_ForecastEndDate , however because of the time element of the date field, projects that are scheduled to to complete on the authorized date, but the time shows later than the 8 am from the custom date, they are showing late.  How can I either ignore the time part of the datetime filed in a formula, or set the authorized date's 'time' to 23.59 in the formula.