The IRS rules are for who the nights are spent with. If the child spends 4 nights with one parent and 3 nights with the other parent, the parent who has the child 4 nights is the custodial parent who can claim the child. So the question for the original poster is whether the child spends 4 days each week or 4 nights each week with which parent. See p. 29 of IRS Pub. 17 under Custodial parent and noncustodial parent. <a href="
http://www.irs.gov/pub/irs-pdf/p17.pdf" rel="nofollow" target="_blank">
http://www.irs.gov/pub/irs-pdf/p17.pdf</a>
