Fix date filter submission
Fix date filter submission

This was broken in the markup changes in the following commit:
dd5ba544f8e9ef8526ba446ab9872e289c80ea0f

alphagov/whitehall,alphagov/whitehall,hotvulcan/whitehall,ggoral/whitehall,hotvulcan/whitehall,robinwhittleton/whitehall,robinwhittleton/whitehall,hotvulcan/whitehall,alphagov/whitehall,ggoral/whitehall,askl56/whitehall,alphagov/whitehall,YOTOV-LIMITED/whitehall,hotvulcan/whitehall,askl56/whitehall,askl56/whitehall,ggoral/whitehall,YOTOV-LIMITED/whitehall,robinwhittleton/whitehall,YOTOV-LIMITED/whitehall,robinwhittleton/whitehall,askl56/whitehall,YOTOV-LIMITED/whitehall,ggoral/whitehall