How many hours a day do WWOOFers have to help the host? And do hosts have a day off?

6 hours a day and you should check this with each host when you contact them.  Hosts and WWOOFers usually have one day off per week.  The spirit of the WWOOF system is that you will be made to be part of the family or community with which you are staying and they will spend time with you, exchange learning with you, take you with them when they go out to socialise and for recreation.
WWOOF Japan  Honcho 2-jo, 3-chome 6-7, Higashi-ku, Sapporo, 065-0042  JAPAN
E-mail: Contact Form   Fax number from within Japan: (03) 4496-6370    Fax number from outside Japan: +81 3 4496-6370

WWOOF Japan LLP (Limited Liability Partnership)