In 'Settings/Users/Access management' enable the right: 'Enable Happy Hour prices'.
You can configure Happy Hour period in 'Settings/General setttings/Happy Hour'.
Enter your Happy Hour prices in each product form in the 'Discount price' field.
During the Happy Hour period, you will find in sales an 'Happy Hour' button to apply your discounted prices.
To force Happy Hour prices, enable the right in 'Settings/Users/Access management': 'Apply discount prices automatically in Sales period or Happy Hour time'.
Select a product in the ticket, and switch off the 'Happy Hour' button to can cancel the Happy Hour discount.