iphone calendar blackout on March 29

I can't see appointments I make for March 29, 2013. Other dates are fine - work as expected. But when I try to create one on that date, it does not show up on the iphone calendar (I create it on the iphone). I tested against both my Yahoo! calendar and my work exchange calendar. In the Yahoo calendar case, I verified that the appointment does show up on the server (i.e., I see it when I browse my calender directly on the Yahoo web site). But the whole day appears blank on the iphone calendar.