Even if this seems a weird answer, let me explain better.
TrackTime is built using FrameworkOnFramework library and this library has very interesting features.
One of these features is the ability to support multiple versions of Joomla, from 1.5 to 3.0
However, I never tested it, since 3.0 is a STS and a lot of extensions are not yet ready for that.
Give it a try, it should work, but i'm not 100% sure
However, I really suggest you to use the 2.5 version, since it's more stable and will be supported for more than a year