The date duration calculator says 1597 days excluding the start date and the end date from 6/28/1914 to 11/11/1918. Of course, when tallying a war, you would include the start and end date for 1599 days. Why, although they were partial days, they were calendar days of war. This is interesting. There is a long biblical tradition of bad things happening in sets of 40. There is also a long history of bad things happening in sets of 39. For example, a prisoner in the ancient world received a maximum whipping of 39 lashes, because 40 lashes could kill him. Most people believe that Jesus was whipped with 39 lashes as that was the Roman custom of the day.
If 40 is a biblical symbol of trevails and hard times, 39 is the number of the brink of annihilation.
It will be interesting to hear the group's thoughts on this subject.