Start: Tanjirou 13, Nezuko 12
1 year later: Urokodaki stops teaching Tanjirou
6 months later: Sabito and Makomo appear
6 months later: Tanjirou defeats Sabito
(Tanjirou 15, Nezuko 14)
7 days in the final selection
15 days after final selection: Tanjirou gets his sword and starts 1st mission
3 days after 1st mission: Tanjirou meets Muzan
? days recovering from drum house: trio goes to spider mountain
? days recovering from spiders: move on to functional recovery training
5 days from starting recovery training: Zenitsu and Inosuke give up
5-10 more days training by himself (unclear if 10 more or 10 total): Tanjirou starts breathing practice
15 days later: Tanjirou talks to Shinobu
10 days later: Tanjirou breaks the gourd
9 days later: Zenitsu and Inosuke learn to breathe
1 month cooped up in the Butterfly Estate (not sure if since pillar meeting or since treatment finished; also doesn't add up to the previous 5+5+15+10+9 days so may just be an estimate)
4 months since train arc: red light district arc begins
1-2 days after infiltrating the houses: Zenitsu meets Daki
1 day after Zenitsu disappears: UM6 fight
2 months after UM6 fight: Tanjirou wakes up
1 week after Tanjirou wakes up: Tanjirou fully recovers
1 day after arriving at swordsmith village: Tanjirou meets Tokitou
7 days after starting the doll training: Tanjirou strikes a blow
1 day after finding the new sword: Tanjirou eats with Genya
1 day after Tanjirou eats with Genya: UM4 and UM5 fight ends, Nezuko in the sun
7 days after UM4-5 fight: Tanjirou wakes up, pillar meeting
? days after pillar meeting: pillar training for the marks
4 days after Tanjirou visits Giyuu: Giyuu talks about Sabito
7 days after Tanjirou visits Giyuu: Tanjirou starts pillar training
10 days after starting training: Tanjirou completes Uzui’s training
5 days after Uzui: Tanjirou completes Tokitou’s training
4 days after Kanroji: Tanjirou completes Iguro’s training
1 day after Iguro: Tanjirou fights Sanemi
6 days after trying to move the rock: Tanjirou talks to Genya
1 day after talking to Genya: Muzan attacks