I am putting together an 0.5 timeline because the events in the past just fascinate me dearly. It is quite hard because it requires skimming through the whole novel. Please let me know if there is a mistake somewhere.
15 years old: Mo Ran became Chu Wanning's disciple and a few months later, he was planted with the Flower of Everlasting Hatred.
19 years old: Shi Mei "died", Mo Ran started to secretly learn the Zhenlong Chess Formation and created the Shared Heart Formation.
20 years old: Mo Ran started his conquest with Sisheng Peak then Rufeng Sect.
Speculation: It is unclear when the siege on Rufeng Sect happened but it is safe to presume it would have been some time after Sisheng Peak got destroyed. In chapter 1, Xue Meng mentioned Chu Wanning once waited for Mo Ran to return all alone days and nights (it could mean a very long time).
Chu Wanning was present when Ye Wangxi was killed so it's likely that the battle between him and Mo Ran happened at Rufeng Sect. Then it would have happened closer to his coronation day.
22 years old: Mo Ran announced himself the new ruler of the Cultivation World. He also married Chu Wanning and Song Qiutong the same year.
So many events we learned about happened within the first year he became Taxian-jun: capturing Chu Wanning, the coronation day, Chu Wanning begging for Xue Meng's life, to their wedding.
Speculation: When did Chu Wanning find out about the flower? I found a hint - Song Qiutong resented "Chu Fei" because Taxian-jun once came to her because he was furious to find the letters Chu Wanning wrote to Xue Meng. This was before Taxian-jun celebrated his third year of being the emperor. So Chu Wanning must have made the discovery within the first two or three years after being captured.
25 years old: Taxian-jun got in a good mood since it was the three year anniversary of being the emperor and being married to Chu Wanning.
Their interaction was much different from other flashbacks, more peaceful and loving. Also, Taxian-jun referred to Chu Fei as his beloved and favored consort. And I like to think they had a bit over five years with moments like that every now and then.
30 years old: Xue Meng's assassination attempt happened. Taxian-jun laid waste on Taxue Palace. Chu Wanning passed away.
A piece of him then spent 8 years longing for the love he thought had abandoned him.