Here is another tip for those who want to sync GTDify tasks with Google calender. Using iCal feeds of GTDify, you can easily export your due tasks to Google calender. Just follow these steps:

1. Navigate to the menu View > Calender in GTDify
2. Right click on on iCal button at right side of the page and copy the location (Copy Link Location in Firefox; Copy Shortcut in IE) of the GTDify calender.
3. Now in Google Calender, click the Add down-arrow button at the bottom of the calender list on the left side of the page, and select Add by URL
4. Paste copied iCal location in textbox and click Add Calender

Google calender will read the GTDify calender and import all tasks which has due-date. Please note that this is one-way task synchronization. Marking any task as done in google calender will not update automatically in GTDify.