Reported on the forum
if i was on the Dashboard of the new site on "today" and then i go to All sites, i am not able to select a date before today because the calendar doesn't offer any links on thoses days.
As a "workaround", i just need to go back to the dashboard, select another site from the site selection drop down (that is stil a bit buggy for me) and then return to All sites and i'm able to back track the stats.
Two things to fix:
(In ) Fixes #1087
Minimum date in the calendar on the All Websites dashboard is the min date across all websites