Neither do I. That doesn't stop me singing it most years! It's a song. It's very old. It isn't even English. But - wikipedia says a better translation might be 'long long ago': https://en.wikipedia.org/wiki/Auld_Lang_Syne

Hi Nelson: The translation means: long long ago, old times, or days gone by. It is a Scots poem, so it may not seem familiar to you. Normally, you hear it during America's New Year's celebrations. Sung before midnight. You may hear it at other celebrations like graduations, or funerals. Hope this helps!

This expression is not standard modern English but from the dialect of Lowland Scots. The literal equivalent words are "old long since" which doesn't make sense in modern English. The meaning is "(since) ancient times".