On previous sites, before ever using C5, I've used a stand-alone calendar (php/sql). So far, I haven't found anything comparable made specifically for concrete -- everything here regarding calendars seems quite overkill for the basic needs of most of my clients.

I had gotten as far as getting rid of the separate login and piggy-backing on the C5 cookie working. It still uses its' own database, which I'm fine with.

After the last update (or before the last two -- I don't remember. I think they both came out within a few days?) it broke the single-sign-on that I had working, and it appears that concrete changed the way their cookie works, or changed their login completely, because we can no longer get the calendar admin pages to authenticate via the cookie (or pull any cookie data, such as test variables, etc.).

Any thoughts? I'm sure you'd need more info to actually help with anything specific, but right now I'm just looking for what might have changed with the c5 login/cookie(s).

Note: Reverting back to the old version DOES allow it to work again.