When using event.module with JSCalendar (part of jstools module), you might experience problems with event times being stored incorrectly. This appears to be due to an obscure configuration requirement when using JSCalendar - apparently, the event module must be configured to use 12 hour format. (This one bit me in the behind today, so I thought I'd jot this down somewhere...)

Be sure to set event.module time notation to 12 hour format:
administer >> settings >> event >> "Time Notation Preference" = 12h

Related info:

http://drupal.org/node/65125#comment-106269