It's slightly confusing as your code refers to 'week_special_rate' but the field in your table is named 'special_offer'..
Anyway, I believe you need a query like:
SELECT special_offer FROM yourtable WHERE `date` > NOW()
or
SELECT special_offer FROM yourtable WHERE `date` > NOW() and special_offer > 0
It might be more complicated if your 'date' field is a string.
BTW (Personally) I wouldn't use 'date' as a field-name - it can only lead to trouble or confusion later