Personally, I would change the database design and instead store the information in a format where it is actually usable.
For example, you might use an integer column to identify which day of the week a given row describes - similar to the [man]date/man format - as well as two TIME columns do identify the start and end times on that day.
That way, checking for overlapping ranges would be a couple of simple numerical inequalities in the SQL query. That is, of course, assuming that I even understand your question at all (which is questionable, since it was a bit hard to understand exactly what it is you're trying to do).
