It would be an exceedingly bad idea to try to capture 2 dates in a single field.
You'd do much better to create 2 column on your table:
startbydate
endbydate
Then you would
SELECT *
FROM someTable
WHERE startbydate>=current_date()
Or if the user were to provide
$startOfMyAvailabilty
$endOfMyAvailabilty
SELECT *
FROM someTable
WHERE startbydate>='$startOfMyAvailabilty'
AND endbydate <=$endOfMyAvailabilty'