why isn't this expression finding whitespace after the date?

I'm using sed to find any expression that matches a date in the format 00/00/0000 with any amount of whitespace after and simply replace it with the letter h. I made the expression:

sed -E 's/[[0-9][0-9]/[0-9][0-9]/[0-9][0-9][0-9][0-9][[:space:]]]/h/g' dates-input.txt

but is not working. help me please