To enter specific dates you can either use the calendar and scroll through to the dates you want, or type in the dates yourself.
24 hours refers to plenary debates within the last 24 hrs or reports of committee meetings that were published in the last 24 hours (the meetings themselves will have taken place earlier).
You can also search by Session. This is the period from the date of first meeting of the Parliament following a general election until it is dissolved. A Session normally lasts just under four years.