the u2.com site shows said 12pm est:
July 2 Chicago (United Center) and July 30 NYC (Madison Square Garden)
eXPERIENCE Group Pre-sale – Wed, Feb 4 (10am)
iNNOCENCE Group Pre-sale – Thurs, Feb 5 (12pm EST / 11am CST)
End Pre-sale – Fri, Feb 6 (5pm)
On sale London - Tues, Feb 10 (10am)
But...