At 13:02 minutes in, there is an office scene. A character opens a windows 10 laptop which shows the date as 22nd May, and the time as 1:19PM, both of which would be incorrect if this were taking place less than an hour before the purge, which is meant to happen on March 21st every year. This was likely the actual time this was filmed, and the laptop clock and calendar were not adjusted for continuity.
The sun is setting at 6:10pm, and is apparently bright at the abandoned building. It becomes quickly dark by 6:22pm.