support of xep-202 ( EntityTime )
XEP-0090, already implemented in gajim, is being replaced by XEP-0202, that provides a similar but different way of reporting the timezone data. As the xep recommend to implement it as soon as possible,here is a small patch that add the missing support.
At the time of writing, the xep is still considered as Experimental, so maybe the attached patch should not be applied right now, and it can serve as a basis in case the protocol change before being seen as draft.