Batch mv or rename in bash script - append date as a suffix - bash

Question

After much searching and trial and error, I'm unable to do a batch mv or rename on a directory of files. What I'd like to do is move or rename all files in a directory so that the mv'd or renamed file has $date (+ '%Y%d%m') added to the original suffix.
All the original files have unique prefixes but are either .xml or .txt so I'd like to go from org_prefix.org_suffix -> org_prefix.org_suffix.DATE
I've tried this:
$ mv /directory/* /directory/*$(date (+ '%Y%m%d')
but always get /directory/*.actualdate' is not a directory error.
I've tried this:
$ for f in *; do mv $ $f.$(date +'_%m%d%y'); done
but I get mv: cannot stat '$'; No such file or directory
Lastly, I've even tried this:
$ rename 's/*/.test/' *
just to see if I could change all the files to org_prefix.test but nothing happens (no errors, nada, zip)
Any help greatly appreciated.

Answer 1

The proper way to loop through files (and e.g., print their name) in the current directory is:
for file in *; do
echo "$file"
done
How will you append the date? like so, of course:
for file in *; do
echo "$file.$(date +%Y%m%d)"
done
And how are you going to do the move? like so, of course:
for file in *; do
mv -nv -- "$file" "$file.$(date +%Y%m%d)"
done
I've added:
-v so that mv be verbose (I like to know what's happening and it always impresses my little sister to watch all these lines flowing on the screen).
-n so as to no overwrite an otherwise existing file. Safety first.
-- just in case a file name starts with a hyphen: without --, mv would confuse with an option. Safety first.
If you just want to look through the files with extension .banana, replace the for with:
for file in *.banana; do
of for files that contain the word banana:
for file in *banana*; do
and so on.
Keep up with the bananas!

Answer 2

$ mv /directory/* /directory/*$(date (+ '%Y%m%d')
This does not work, because the * is expanded to a list of all files, so after the expansion the command will be something like:
mv /directory/file1 /directory/file2 /directory/file3 /directory/file1_date /directory/file1_date ...
So you have specified many destinations, but the syntax for mv allows only one single destination.
for f in *; do mv $ $f.$(date +'_%m%d%y'); done
Here you forgot the f after the $, that's why you get the error message.
for f in *; do mv $f $f.$(date +'%m%d%y'); done
I think this should work now, but don't forget to quote all the variables!
Finally:
for f in *; do mv "$f" "$f.$(date +'%m%d%y')"; done
Edit: When there are characters directly after a variable, it's good practice to use {} to make clear that they are not part of the variable name:
for f in *; do mv "$f" "${f}.$(date +'%m%d%y')"; done