Generally speaking you should be able to pattern this using something like INDIRECT combined with other formulas. There are a number of ways to approach the increment. You could either hard code the start date in the formula or place the start date in a cell someplace, then simply start date + 7x, where x could be row number (starting from a reference to row 1). That would effectively add the n number of days to your start date needed and INDIRECT would be used to create the reference based on this.

As mentioned you may consider an option like Power Query and/or leverage a data model.

Another alternative would be a macro to simply gather data from all the files in a given folder.

Many ways you could handle it, hard to say whats best without more context.