Just did both my own and my father's 90 days online, on the website. Both took only a few minutes and got approved on the spot. We have saved the receipts and printed them.
It doesn't say when the next due date is. Even though I am perfectly able to count to 90, I am just in doubt if it should be counted from today, or from the actual due date which in this case is 19th of May.
TLDR : Answer Summary
The user successfully completed the 90-day online reporting for himself and his father, but is uncertain about how to calculate the next due date. The main question is whether to count the next 90 days from the date of submission or from the previous due date of May 19. Comments from others provide reassurance that reporting can be updated through the online program.