Office hours are Monday-Friday, 2:15-2:55, Philadelphia time (usually GMT-5, although it can sometimes vary, depending on idiosyncrasies of daylight savings times), in McNeil 519 or by phone at +1 (215) 898-1507. I give priority to those physically present and switch the phone to voicemail when in a meeting.
Known days when I am away, with no office hours, are posted here. Additional cancellations/modifications include those listed immediately below (if any).
Offfice hours by appointment 4/29/2013 onward.