We've updated our list of reporting dates after teams made some subtle changes to the schedule for Spring Training 2013.
If you've made some plans to attend the first day of practice -- which is the day·after·reporting day -- you should check out the list. What happens: many teams announce their spring-training schedules and at the same time announce a tentative reporting date. We track those.
However, teams don't make big announcements when they change the reporting date, and many did indeed make some changes. So if your plans hinge on being around the first day players hit the training fields, take a look and verify that you've got the correct date in the calendar.