Recent Hitwise traffic data on Google Calendar is out, and it shows a steady increase v. the competing products from Yahoo and Microsoft. All three are about the same size now, although only Google Calendar is pointing in the right direction.

I recently switched away from using Mac Calendar after too many struggles with synchronization. I still view my calendar from the Mac desktop application, but all the data is stored at Google and read/write access is shared with the team. I’m not surprised to see it getting traction against Yahoo and Microsoft – those guys haven’t put much attention into their own products lately.

As we did a couple of weeks ago with Google Blog Search, we also took a look at the most recent Comscore data for the three products to see what they have to say. I’m surprised to say that Comscore is showing the same trends and overall rankings as Hitwise, something that rarely seems to happen. Comscore still shows Yahoo solidly in the lead, but declining rapidly.

Charts below.