Is it really that tough?
- First great Ninja war happened post Hashirama death and when Tobirama took the reigns of Hokage.
(Unknown time when started), ended with death of Second Hokage
20 years of peace gap.
- Second Great Ninja war, uprising from Amagakure, The legendary Sanin made their Debut, Tsunade lost her Lover. Sakumo also made his debut here.
Maybe 10 years before the main timeline started.
- Third Great Ninja War, War Heroes like Minato, Ai showed up. Kakashi and Obito tragedy.
Maybe around 20~ish year later.
- Obitk declared fourth great Ninja War.
You can track it by Hiruzen.
- Hiruzen was 20 when he became Hokage,
- after 20 years, Hiruzen was 40, when Second great war started.
- Kakashi waa 26 in Naruto, and Hiruzen was 68, if Kakashi was 14 during the end of war, Hiruzen was around 56 years old.
So putting it on a timeline.
- 20 year old Hiruzen (End of First great Ninja war)
- 40 year old Hiruzen (Start of Second great Ninja war)
- 56 year old Hiruzen (End of Third great Ninja war)
- 70 yeae old Hiruzen (If Alive) (Start of fourth great Ninja war)
All this happened in the span of 50~60 years timeline.