vdirsyncer: synchronize
calendars and address books, including data from khal and todoman
pimsync: re-implementation of vdirsyncer
addressing outstanding issue and limitations.
These programs are build around existing standards formats and protocols, and
use the vdir storage format to store data on a local filesystem. The
vdir specification builds atop existing standards, and allows applications
from different authors to operate with the same set of locally stored calendars
and address book.