Opening hours for vendors and related search filter

Hello,

Unfortunately there is not a simple solution for that.

With HikaShop 3.x, there is a new plugin for the shop open hours. That plugin is using the multi-instance system so you can create ranges regarding the shop.
Implementing such thing for the vendor would require some interfaces in the front-end to let the vendor perform that configuration regarding their open periods.

Afterwards, there is still the possibility to use custom field.
Thanks to custom plugin, you can create your own kind of field. Which mean that you can have a specific interface for the field edition and you can also have some control on the field saving (so you can serialize the data).

Last part of your request is to have a date picker which would have the knowledge of the products in the cart (and its vendors) so it can disable closed days.
Since an order custom field do not have an access to the entire cart/order ; it would also require some development in order to retrieve that information (you can get the current cart id or check the parameter which can be passed in the checkout URL when customer wants to checkout a cart which is not its current cart).

The usage of serialized data is interesting because the edition interface would be centralized. But the side effect is that you can't use the data easily for SQL queries.
So if you want to have a dynamic filter in product listing, you would have to split the data into several columns or to format the data in a way that you can use it with SQL.

At the end, the best way to implement this is mostly to know what would be your needs (features).
Depending the interface you want for your vendors and the asked elements (how many date range, how the day and date range selection are made, etc) ; you would have enough specification to choose an implementation path.

Regards,