I don't know if the date itself has any significance but the 13th was Friday. However if you wanted to go for maximum psyops points you would stage the attack on the 9th of November, which would be 9/11 for Europeans. That way your attack would bring back the memories of 9/11 every time 90% of the time.

Battlefield confirmed for terrorism plot.

The ragheads probably used it to train/plan.