The date format will be set automatically based on the user current language.I know that it can be complicated, but this complexity is being added by the hotelier, IOSR can support that. This is the important thing.Most hotels have simple rates. But if you have rates that goes up and down every day like shares on a stock exchange it is not IOSR that adds the complexity, it is you.
The "not available" checkbox has been discontinued in v3.5. Now, to make a room not available you just set the "vacancy" for that period to 0 (see screenshot). It wont take you more than 10 seconds to add a new season with "stop sales".
You have first to modify the 2 existing seasons and make them:from 2010-08-01 to 2010-08-19from 2010-10-11 to 2010-11-30and then add a new one:from 2010-08-20 to 2010-10-10 with vacancy = 0