I like what your doing there, maybe the colour scheme is a bit dull?
Why's everything not alligned?
there's a massive gap between the nav and the content, and the way the header is sectioned up doesn't logically guide the eye to anything, just seems a little random
I like the background of the header. maybe the layout would look nicer if you used that same type of background for the subheadings.... to keep a consistent theme. I like the date button btw, it really goes nicely with the theme.
The background of the bar that the subheadings are placed on - where it says "Navigation" and "Unexpected Error" - looks tacky, probably because the gradient is too steep and that clashes with your lovely soft header

look forward to seeing it when its done