These calculations were not dropping the time from the provided date.
And so a week would be Monday 11AM to Monday 11AM when run at 11AM.

BUG=


Review URL: https://chromiumcodereview.appspot.com/11233041

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@163360 0039d316-1c4b-4281-b951-d872f2087c98