I am new to calibre (downloaded this weekend) and have a similar problem.
I have been a Baen Webscriptions subscriber for many years. When I started, I reviewed the available readers and settled into the Microsoft Reader. I have not looked much into it since then, but have still no complaints about the Reader or its Library function.
I recently got an iPad so am looking for ways to read my books using it. I reviewed some readers and like the iBook reader best (personal preference). I downloaded some books from Baen in ePUB format and think the iBook reader is satisfactory for them.
I am now trying to get my existing library imported into calibre. My books are in .lit format and are all in a single directory. I was able to import it into calibre and was then able to convert some books into the ePUB format easily enough. That is all fine.
The Microsoft Reader can sort the library also by Date Acquired. I use that quite a bit. I think the equivalent is the Date column in calibre. But on my imported books the Date column shows today's date. I looked at the source a bit, and it looks like the Date column is only a timestamp taken during the import.
What I would like is to be able to modify the Date column in a batch mode from a directory listing of my old books so the Date column would show the date I originally acquired the book, not when it was imported into calibre. Does anyone know how I could do that? I am new to all this and am currently thinking of either using the calibredb interface or writing a recipe. Any opinions would be welcome.