Themes.tikiwiki.org is running 1.9.9
Calendar has been reworked in 1.10 and is considered "better"
Maybe you should "use tabs" in the themes or look & feel admin panel.
The feature is there, somewhere, just need to turn it on.
We avoid making unreleased modifications. We only do when it's really unique, like the theme-o-rama module. And it's always available on demand.