You must have seen this message show up as you start SOLIDWORKS 2015 SP0:
If you have a custom property for the date created in your part, drawing, and/or assembly, you may want to upgrade to SP1.1. The problem will cause the date in that custom property to roll back a day every time you open the file. It's just good practice to upgrade even though you don't use that custom property.
For those of you who have access to SOLIDWORKS 2015 SP 0, but do not have access to SP1 or newer, SOLIDWORKS will give you access to download and upgrade to SP 1.1. Please contact your SOLIDWORKS provider if you need access to the files.