Thank you everyone.

I have gotten paystubs that correspond with the time of the move.  

The thing that got me to look into this further was that both the husband and the wife's employers withheld in the employer's states once the taxpayers moved to Delaware.  One is a federal government agency that is in Maryland.  The other is a huge government contractor in Virginia (this withholding changed from MD to VA when notified of the move).  At first I thought that both had mistakenly withheld for the wrong states but that bothered me too much to let it go.  The likelihood that they were both wrong and I was right was just too small.  🙂

This is for next year so there is plenty of time for me to figure it all out.