On a completely different subject, I have been working out the dates given in the book as opposed to those given in the series set decoration. Gaiman had removed those dates from the Script book, but someone doing set decoration put them back in the filmed Series. I think that was a mistake. This story is mythic, and is always set to happen "next Saturday". Putting a precise date on it ties it to a calendar, and authors notoriously don't check calendars when they are writing. Furthermore, the standard calendar changes in regular ways except when it doesn't; not only do leap years change how dates and day-names fall, so do periods of 400 years and millennia change how leap years fall.
Given that in the original novel, the paintball training session was held on August 20 and 21, and it happened at some point after the Antichrist's eleventh birthday which is on a Wednesday, I looked carefully at the specified timing of events. In the novel, the paintball fight is going full-on at night (unusual, I believe), and happens a day earlier than in the script, when it is going on in daylight. That changes the timing of a few other things as well. The series as filmed seems to match the script pretty well as far as that goes. Unfortunately for the fans who want precise dates, Gaiman said on one occasion that it happens in 2018 and on another that it happens in 2019.
To make matters worse, those given dates don't work for either of those years.
The paintball fight has to happen during the time period of August 20-21. If it is at night, it has to be on August 20, late at night. If it is daytime, it happens on August 21, because otherwise it's too fully-engaged to be early in the morning on the first day of a two-day conference.
Book-canon timing of events with a night-time fight requires that Armageddon happen on Saturday, August 22. That date happens in 2009 and in 2020.
Script-canon* timing with a daytime fight requires that Armageddon happen on Saturday, August 23. That date happens in 1986, 1997, 2008, and 2031.
So, any writers out there: either check your calendar carefully, or make your story timeless and undatable. Because people will check.
*Technically, it's Series-canon, because the dates were removed from the Script but visible in the Series. But since I don't have access at the moment and have to rely on my memory (I do recall the paintball fight being daytime), I'm calling it script-canon.
ETA: sigh. I should never post anything involving numbers. Right now I think I reversed some of the date information. But it is true that the book differs from the script about the time of day of the paintball fight. In the book, it's around midnight Wednesday night, the same day as the birthday but well after 3 PM, and after they run into Anathema. In the Script it's in full daylight, and our two heroes leave as it is growing dark again, and only then run into Anathema.