Ok, may be totally not related but we had a april fools day problem with this widget. Entering the first of april resulted in the 31st of march in the database. I could not believe this untill I saw it with my own eyes.
But we could not reproduce this in another project. We really thought somebody pulled a practical joke, but since no way to reproduce this we did not do anything with it.
Did you check the timezone setting of the user vs timezone setting of the application?
Could there be a bug somewhere with DST in this widget?
Regards,
Ronald