#!/bin/bash

for file in *; do 
    ## Skip unless this is a file
    if [ -f "$file" ]; then
        ## get the first four characters from filename, aka the year
        target="${file:0:4}"
        ## Create the target directory if it doesn't exist
        [ -d "$target" ] || mkdir  "$target" 2>/dev/null 
        ## Move the current file
        mv "$file" "$target" 2>/dev/null
    fi
done