When did the new national anthem replace the old one

I think there may be some confusion here!

The United States has only had one national anthem, "The Star-Spangled Banner", since its adoption in 1931. There has been no "old" national anthem replaced by a "new" one.

"The Star-Spangled Banner" was written by Francis Scott Key in 1814 and was originally a poem titled "Defence of Fort M'Henry". It was later set to the tune of a popular British song, "To Anacreon in Heaven", and became known as "The Star-Spangled Banner". It was officially adopted as the national anthem of the United States on March 3, 1931, by an act of Congress.

So, to answer your question, there hasn't been a replacement of a "new" national anthem for an "old" one, as there has only been one national anthem in the United States since 1931.