Backup files that file is older than a month ago.

move_older_than_a_month_ago.sh

#!/bin/sh

SOURCE='/path/to/source'
  DEST='/path/to/backup'

TARGET="$DEST/$(date +'%G%m')"

mkdir -p "$TARGET"

function copyext() {
    loval TABC=$'\t'
    local FILE=''
    local MODDATE=''
    local LTEDATE=$(date -d '-1 month')
    for FILE in `find "$SOURCE" -name "*.$1"`
    do
        MODDATE=$(date -r "$FILE")
        if [[ $MODDATE < $LTEDATE ]]; then
            mv $FILE $TARGET
            echo "$FILE$TABC > $TABC$TARGET"
        fi
    done
}

copyext 'txt'
copyext 'log'