Oh. OK. Sorry for misconstruing your intentions. I think that could probably be done, but at the moment I suspect it would be a DIY solution, since Tris is quite busy at the moment.
Zenphoto already has a rudimentary date function in the latest 1.0.3 version, and I do have it enabled in my code on my site, but I don't regularly use it. My Thinkdreams theme took advantage of displaying it, but my new theme does not.
As for building a calendar, or timeline, if you will, you could take the functionality and create a PHP based 'timeline' display of the pictures in chronolgical order.
If you do a search for 'timeline wordpress php' there is a wordpress plugin that displays a timeline that was recently done, that might be able to be adapted for this purpose.
Since you're just pulling date information already in the Zenphoto DB (if you enable the date functions commented out in the current version), you should be able to do what you want. Provided you wish to mess with the code.
Just some ideas. Pardon my rambling.