The IRS in Publication 17 also says:
"Parent works at night.
If, due to a parent's nighttime work schedule, a child lives for a greater number of days, but not nights, with the parent who works at night, that parent is treated as the custodial parent. On a school day, the child is treated as living at the primary residence registered with the school."
<a rel="nofollow" target="_blank" href="
https://www.irs.gov/publications/p17#en_US_2017_publink1000170897">https://www.irs.gov/publications/...>
**Disclaimer: This post is for discussion purposes only and is NOT tax advice. The author takes no responsibility for the accuracy of any information in this post.**
