The move, to be announced internally later today, is not a big surprise, even though Yahoo paid $350 million for Zimbra in the fall of 2007.

Dharmaraj (pictured here) had previously stepped back from day-to-day leadership at the Yahoo communications and communities division, which is run by former Zimbra President and CTO Scott Dietzen.

But the departure of an innovative entrepreneur like Dharmaraj–although typical when big companies buy start-ups–is never a good thing, given that it’s more important than ever to keep innovative leaders at Yahoo.

New CEO Carol Bartz will have to tap internal leadership if she hopes to turn Yahoo (YHOO) into the kind of fresh opportunity she said it could be when she was hired earlier this month.

Yahoo introduced new email services recently, based on some of Zimbra’s technologies and concepts.

That has been important, since Yahoo Mail has always been a company bright spot and has remained the bigger provider of Web email to general consumers.

But most agree that Yahoo has allowed the Google (GOOG) mail offering, Gmail, to suck up all the oxygen in the room with more flashy features like threading of conversations while not serving up a strong response quickly enough in an arena Yahoo pioneered.

Zimbra vaulted its effort at differentiation from the hyped Google offering forward more quickly.

More importantly, it has strengthened Yahoo’s ability to make online email act more like a computer program than a Web page, which has been the main focus of late of Yahoo, Google, Time Warner (TWX) online unit AOL and Windows Live Hotmail from Microsoft (MSFT).

In addition, since Zimbra was designed with flexible and open Ajax programming tools, it made it easy for third-party developers to make many other applications that jack innovation from the outside, making the communications platform the center of the Web experience with video, search and other tools.

It’s not clear where Dharmaraj is going, but here is a video interview I did with him last year after Yahoo bought Zimbra:

In its ongoing renovation of its offerings–last month it began rolling out a new homepage–Yahoo is unveiling a new online calendar, with a passel of new bells and whistles, to a small group of users worldwide.

At first, the beta–current users can register to try it here–will take place in the United States, Brazil, India, Taiwan and the United Kingdom.

Overall, it is a good-looking, simple and clean design–that will eventually be extended to all of Yahoo’s 8.1 million calendar users worldwide.

It is also Yahoo’s first attempt at leveraging and integrating technology from its $350 million acquisition of open-source email and calendaring company Zimbra just over a year ago.

And, incredibly, although Yahoo’s is the top online calendar in the world, it has been 10 years since the Internet giant updated it.

That lack of innovation has resulted in major inroads in recent years by newer entrants like Google, whose calendar launched with more modern features, like color-coding, easy sharing and drag-and-drop functionality.

With its renovation, which is based on open standards, the updated calendar from Yahoo (YHOO) now has these kinds of features and also works more seamlessly with Yahoo’s powerful email product, Yahoo! Mail, which has 278 million users.

The new Yahoo calendar is built on the Zimbra platform, which uses Ajax functionality in its online calendars and iCalendar (iCal) and CalDAV3 standards.

That makes it interoperable with other online calendar services, including those from Mozilla, Apple, Microsoft, Time Warner’s AOL and Google.

One of the cooler features is the ability to zoom-in and zoom-out from a monthly wall calendar view to a single event.

In addition, Yahoo’s new calendar can integrate pictures from its Flickr photo community and also has a “to-do” list.

As the beta is rolled out further in the coming months, Yahoo will add additional synching and event discovery features.

I talked about all this today with Yahoo SVP Scott Dietzen, who came to the company with the Zimbra acquisition and now is in charge of all communications products at Yahoo.

Here is the video interview I did with him:

And here are the screenshots of the new calendar, along with one of the old calendar, for comparison (click on images to make them larger):

The old main Yahoo calendar

The new main Yahoo calendar

The “zoom” feature

The integration with Flickr

The Upcoming.org integration