Usually there are disagreements as to the exact dates of beginnings of conflicts, especially when those conflicts are global.
“The beginnings of wars are often hard to identify. Which act lit the spark on the tinderbox? Which straw was the final one? Like peak oil itself, the beginnings of war are often visible only in retrospect.”
For example, some would argue that World War II began in 1939 with the German invasion of Poland. Others would pick the 1931 Japanese invasion of Manchuria, or maybe even the 1933 Reichstag Fire. The only consensus regarding World War II is that it was devastating.