We're nearing the end of 2012, and that means Google is doing some "winter cleaning" around the office and some less-popular services are going away. Google will be shutting down several services related to sync and calendar, all within the next month. First, several Google Calendar features are going away -- reservable times can no longer be created in appointment slots, but currently set slots will remain for one year. Two calendar "labs" features are going away as well: "Smart Rescheduler" and "Add gadget by URL." Google is also removing features that let users check and make appointments via SMS.
Next, traditional Google Sync is going away -- this was the protocol that let users sync their mail, contacts and calendar to devices via the Exchange ActiveSync protocol. With the introduction of CardDAV and CalDav, Google can now offer much the same service with the IMAP protocol instead. Google Sync will shut down to new users on January 30, 2013, but will remain active for anyone that sets it up prior and all Google Apps users.
It sounds like a doomsday scenario of Google services getting shut down, but most users won't notice. Android syncs natively with Google Apps and therefore won't be affected by the Google Sync shutdown. You may want to take a look if you happen to use any of these Google Calendar tools, though.
Source: Google Official Blog