In Scheveningen (and in the indoor shopping mall Palace Promenade) the shops are open every day, 365 days a year.
Furthermore also the shops in the center of The Hague are open every Sunday.
The upcoming local shopping opening hours in Scheveningen during Sundays and public holidays (like Easter, Pentecost, Christmas, etc.), can be found at the following website: http://koopzondagen.net/koopzondag/Den%20Haag.html
The standard opening hours in Scheveningen during Sundays and public holidays are of 12:00 till 17:00 hrs.