Thanks for the explanation, it makes me content to understand why this is happening even though I can't correct the problem.

I usually use Firefox to use the Google calendar, but it works on all the other browsers I have installed on my computer - Chrome and Internet Explorer as well. That's an interesting explanation, I guess it's not something I could do anything about though.

I don't really have that many extensions either. I only use uBlock (an adblocker) but I had this problem with Google calendar and some other sites before I ever even installed that. Thanks for the clarification that it's not a common problem at least.

Ever so often, I experience cookie problems while using Opera (version 33.0). For instance I have never been able to open Google calendar - I get a notification saying that there are problems with my cookie settings instead of being able to see the calendar page at all (other Google services like Gmail seem to work fine). But my cookie settings are normal. I have allowed everything. I have to use another browser to look at my Google calendar which is annoying, but I put up with it because I like Opera otherwise.

That is not the only site I have or have had problems with, sometimes it seems pretty random. Just now I visited a site I don't think I had visited before just to look for a cooking recipe and it told me using the site requires cookies to be allowed.

My question is, why does this happen? Is there some known common problem with Opera and cookies? Am I not doing something right?