[Dart] Dashboard rollover times.

[Brad King]

Jim,

> and minute.  It was once suggested that we hyphenate the build stamp
> so it would be something like 20020108-0400-Nightly.
That shouldn't be too hard.  It just means a few of the offsets for time
lookups need to change.  I'll make the changes on the branch and see what
happens.

> If it all working fine, I'd say put it in the main tree.
It seems to be working so far for Boost, but I haven't tried more than a
few builds.  Perhaps we should switch one of the other dashbords over to
it and see what happens.  Another problem is that both the server and
client have to switch over at the same time because the two encodings are
incompatible.  Actually, if we are breaking compatability anyway, we might
as well rip out the leftover code that supports the "old" style of nightly
build.  Ideas on this problem?

-Brad