They're military, so these "important events" would have been daily topical reports and were, at the time, already world news. There's also no reason to believe they'd only give themselves permission to write in each square during the 24 hour period of the corresponding day.
If Fridays are slow, catch up on the news, ink the notes you penciled in, and find some time to color them when you can. You've got the entire month - and that's a ton of time when you're not someone's productivity slave.
Also, notice the last week or two of each month gets sparser and less complete. That implies to me that they flipped the sheets and didn't go back to work on the old ones. If this were an art project, there wouldn't be a difference between the start and the end of the month.
If Fridays are slow, catch up on the news, ink the notes you penciled in, and find some time to color them when you can. You've got the entire month - and that's a ton of time when you're not someone's productivity slave.
Also, notice the last week or two of each month gets sparser and less complete. That implies to me that they flipped the sheets and didn't go back to work on the old ones. If this were an art project, there wouldn't be a difference between the start and the end of the month.