I can't think of why a significant spike like that might occur on a particular day, aside from some regular differentiation in your usage pattern around that time, like an appliance that is scheduled to run. If you think there might be some issue with the accuracy (such as a meter fault) I'd encourage you to give customer service a call, but the cause is likely to be something simpler than that. Definitely let the community here know when you figure out what's going on!
