I know that marketing isn't always considered canon (apart from in-universe news reports like WHiH), but Sony released an app for Spider-Man: Homecoming including videos and text messages from Peter's phone:
https://imgur.com/a/gFrHX
Some of the things that are mentioned in the text messages are things that happen in the movie, such as the decathlon and Spider-Man stopping a bike robber, and they also feature the day of the week.
Since we know from the ticket prop that September 23 is a Friday, then, if the text messages line up with the span of time depicted in the movie, maybe we could use them to help with the date placements for the movie, as long as it doesn't contradict anything?