Hi Ashley,
Dates should always be stored in a timestamp field - it makes things SO much easier! It will be very hard to compare values in their current format, especially as the field starts with a letter. The ideal layout would be YEARMONTHDAYHOURMINUTESECOND, as it can be easily sorted. I'd really recommend creating a script using mktime() to repopulate the database with timestamps instead.
When you have done this, you can easily grab a timestamp using time() and search for values greater than (time() - 86400) - 24 hours or (time() - 604800) one week.
I really cannot stress how bad the current design of the database is in terms of date manipulation..
Regards,
David