Sorry for the english reply:

• If these are rates you would do this via the Restrictions to block the rate
• If a product - edit the product and untick the option for ‘Offer to Customer’ - you cannot set this just for specific dates, so have to remove and add when needed, but only stops people adding it at point of reservation, so applies to ALL bookings made from the date you remove. So if you want to stop it just for August for example, you can’t.

Best practice to achieve this:

1. Create a new rate that has the product added by a Product Rule
2. Use Rate restrictions to control the dates it can be booked and can’t be booked.

Hope that helps :)