After upgading to latest Sienna 0.9.12.1 from 0.9.9 I got as mentioned weird Date problem.
After editing page (for ex. with 02.02.2012) date becomes 01.01.1979 (in any theme, in form it looks like nothing at all - "-")
The same situation with creating new page - never mind wich date I placed - it became "-" (and in page view - 01.01.1970)
Please, help me - just say where to digg, or what it can be?
thank you, wbr Alex