"too many possible variations" sounds like a reason to me to have the browser support it - to add cross-site consistency to the element. Once you know how the

"too many possible variations" sounds like a reason to me to have the browser support it - to add cross-site consistency to the element. Once you know how the calendar on your OS/browser works, you know how the calendar on all the websites works. Also, adding accessibility for those with visual problems is a job to be performed once, by browser implementors, and can be completely ignored (at least for wrt calendars) by everyone who ever writes a website. Learning keyboard shortcuts becomes worthwhile (or even just possible). Overlaying the events from your personal calendar, say when hovering over a date, would make it possible to easily pick dates that coincide with (or avoid) the holidays associated with your particular culture - which your OS knows about, but J. Random Website doesn't - without leaving your browser. (Not all cultural holidays are as easily predictable 8 months in advance as Dec 25! Think of those based on lunar calendars, e.g. Easter) Heck, I find it annoying when websites want to use custom drop-down lists or buttons. The drop-downs and buttons that my OS provides are beautiful, thanks very much, and easily recognisable to boot. I know just by looking at the page where the controls are and how they're going to act. If I want them to look and act differently, I can change that in one place, in my OS settings, and the controls all change in a totally consistent manner for every website ever written, except those that try to be clever and break my setup instead. I can't believe I've heard some people complain that they thought that the standard controls are "too ugly". Well, get a prettier browser/theme/OS then!