When Felicity's mother's smartwatch chimes, and Felicity asks her what was that sound, she replies that the watch chimes on the hour. Yet a few seconds before when the watch is shown when it just started chiming, it's time as 8:43pm.
An attack on the city comes in the form of transformers bursting, sparks flying everywhere, and all power in the city going down - then the attackers "make an announcement" through TV sets around the city which they would of course not be able to do since they had just blown all of the electricity.