Imagine your online availability table as a 'wheel'. You wheel has 53 spaces. You need to log in to your update page, which you will have a username and password for, and edit the dates.
If you change the week start and week end dates to the next in the 'wheel', as every week passes, you will have a run of 53 weeks all the time.
Your table you see when you view the page on the internet will always show the present and future dates, because as a week passes, it will disappear from the table.
These dates will still show on your editing page, which is why they need to be changed to the date 53 weeks ahead.