GOP and Order Promise Dates: UTC vs local time

Hi

We are struggling to align our delivery-on-promise reporting for customers in the US. Our system database time is in UTC and we have a distribution site in Boston, MA, which is EST. We are observing that order shipped at the end of US working day (7pm EST and later) look as if they were shipped next day (and thus late) when looking at the data in UTC. Have other customers encountered this issue, and what steps were taken to overcome it?