Recently on 26th march, 2013 Google Analytic was showing a jump of visits for all websites [image-1].
But when checked out for specific date only, stats were showing just half visits [image-2].
That stats were only showing double visits for 26th march, other stats are showing actual visits with both conditions (Monthly stats and single day stats).
On 28th march morning at 11:00 AM Analytic was showing same but at 11:30 am Google changed that stats and Analytic showing now actual visits with both conditions for 26th march [image-3].
Google didn’t announce officially yet about double visits on 26th march. Google redesigned Analytic to Improve The Activity Stream In Social Reports on same day (26th March). May be the jump of visits was effected by this update.