The NAV does not change on weekends as the stock market is closed. No body buying or selling, thus the price of stocks does not change.
.I've often wondered why the Stock markets on weekends and holidays freeze,(NAV doesn't move) when many of these corporations are open and operating, making their biggest profits during these time periods?
Most of the headquarters for the major corporations are closed on weekends and holidays. That is where the money making decisions are made.