In my own work I'm primarily interested in practicas and prognostications rather than calendars, which are a very different kind of text, and I'm primarily interested in the late fifteenth and sixteenth centuries, even if recently I've extended my view to 1620, which means that a calendar from the late seventeenth century would not normally hold my attention.
But a complete digitized archive of complete runs of dozens of calendars over several decades, many with accompanying prognostications? That gets my attention.
The digital archive of the Kalendersammlung des Stadtarchivs Altenburg is browsable by title via the UB Jena. There are a few calendars earlier than 1650 and several from after 1700, but the bulk of the collection covers the second half of the seventeenth century. A description of the project is here. (And while you're at Archivalia, be sure to read Klaus Graf's excellent and extensive post on "Christian August Vulpius als Quellenfälscher.") Even without reading the calendars or knowing the authors, I'm confident that there is a lot of interesting research waiting to be done using this archive. An archive that is so unique, thorough, and accessible is a rare and wondrous thing.