Hi,

I just discovered that typical all-day event org timestamp

  <2013-11-19 Tue 00:00>--<2013-11-20 Wed 00:00>

will produce two entries in the org agenda - one for the 19th (expected)
and another one for the 20th (incorrect). It would be similar for any
event ending at midnight.

The enclosed patch fixes the org agenda issue by either omitting the
start/end times entirely (e.g. for all-day events)

  <2013-11-19 Tue>

or by generating end time of 23:59 on the day before

  <2013-11-19 Tue 18:00>--<2013-11-19 Tue 23:59>