According to the release notes, iTunes 11.1.6 “restores the ability to sync contacts and calendar information to your iPhone, iPad, or iPod touch from your Mac running OS X 10.9.3.”
When iOS 7 and Mavericks were introduced back in September, Apple removed local syncing in favor of cloud syncing, allowing users to sync calendars, contacts, bookmarks, and notes only via iCloud. Many users were unhappy with the feature removal and their inability to sync information to their iOS devices using their Macs.