In January, Google released an offline version of Gmail based on Google Gears. Last month, it began offering an offline version of Google Calendar to enterprise app customers. Today, the rest of us get to try the offline calendar, which is also based on Google Gears.
Once you click on the “Offline” link at the top of the page, the application asks you once to enable Google Gears for the Calendar. After you do that, it allows you to read your calendar when you are not connected to the Internet. A Calendar icon appears on your desktop. When you click on it, your browser opens up to show your recent schedule (it only goes back a month). For the most part, the offline version is read-only. You cannot edit existing entries until are back online. However, you can add new entries.
There are obviously some syncing issues going on here, but it seems that Google should be able to figure out how to let you edit your calendar and then sync once you are connected. Without that ability, it is a hampered product. But it is still better than no offline access whatsoever.