Renaming files/dir's from one date format to another - date

Question

So I am a coding newbie and have, for some time, wanted to edit the formatting of my fairly extensive live music library. I have looked around on here and various other resources to get to where I am, but I have hit a snag. I have directories named in the following ways:
02.10.90 | 23 East Caberet - Ardmore, PA
02.16.90 | The Paradise - Boston, MA
and I would like to rename these simply to
1990-02-10 | 23 East Caberet - Ardmore, PA
1990-02-16 | The Paradise - Boston, MA
I have been able to rename the date correctly using:
ls -1 | grep 90 | awk '{print $1}' | awk -F. '{printf "%s-%s-%s\n", "19"$3,$1,$2}' > list1.txt
and then pull the rest of the name using
ls -1 | grep 90 | awk '{first = $1; $1 = ""; print $0}'>list2.txt
So, I have a list of directories ranging from years 1990-2004 that I would like to apply this to (they are all in different sub directories so I don't mind manually changing the "grep 90". However, from the two separate lists that I generate, I cant figure out how to make it loop through each row and print "mv original_name list1.txt+list2.txt" so that it would read:
mv 02.10.90 | 23 East Caberet - Ardmore, PA 1990-02-10 | 23 East Caberet - Ardmore, PA
I scanned through many previous posts and couldn't quite figure out the last bit - or better yet, a more elegant solution! Any help is greatly appreciated, thank you in advance!

Answer 1

Don't parse the output from ls, google why, and you don't need grep when you're using awk, nor do you need chains of awk commands but for this task you wouldn't use any of those commands anyway.
The UNIX command to find files is named find so start with that. This will find all directories with names starting with the given globbing pattern:
find . -type d -name '[0-9][0-9].[0-9][0-9].90 *'
Now that you've found the files you need to do something with them. For your needs IMHO the simplest approach is best and that'd be:
find . -type d -name '[0-9][0-9].[0-9][0-9].90 *' -print0 |
while IFS= read -r -d '' old; do
path="$(dirname "$old")"
oldDirName="$(basename "$old")"
if [[ oldDirName =~ ([0-9]+)\.([0-9]+)\.([0-9]+)( .*) ]]; then
newDirName="19${BASH_REMATCH[3]}-${BASH_REMATCH[1]}-${BASH_REMATCH[2]}${BASH_REMATCH[4]}
echo mv -- "${path}/${oldDirName}" "${path}/${newDirName}"
fi
done
The above is using GNU find for -print0 and bash for BASH_REMATCH. Remove the echo when you've debugged it if necessary and are happy with what it's going to do.