Correct usage of variable name.

host.yaml

@@ -11,7 +11,7 @@
     - debug: var=ansible_date_time.iso8601_basic_short
 
     - name: Backup mysql databases
-      shell: docker exec mysql8 mysqldump -u{{ mysql_user }} -p{{ mysql_password }} {{ item }} > /home/chris/{{ item }}_{{ ansible_data_time.iso8601_basic_short }}.sql
+      shell: docker exec mysql8 mysqldump -u{{ mysql_user }} -p{{ mysql_password }} {{ item }} > /home/chris/{{ item }}_{{ ansible_date_time.iso8601_basic_short }}.sql
       loop:
         - bookstack
         - kimai