A while back, someone posted a theory that this story is about the 19 days before Jian Yi ...

A while back, someone posted a theory that this story is about the 19 days before Jian Yi disappeared so I reread everything to see how many days has passed. Depending on interpretation (explanation below), 10 days have passed since the "middle school" chapters started. 8 school days if we skip the weekend and maybe 7 days because Old Xian might have messed up on He Tian's dialogue at one point. More details below:

The first few chapters were obviously after Jian Yi returned so I started counting in the chapter where Zheng Xi was avoiding Xiao Hui (girl who has a crush on him) as Day 1. However, the middle school uniform does not show up until the 2nd day after that chapter so the "first day" is up for interpretation.

Then comes the weekend (+2 days, Day 3-4) where Zheng Xi has the wet pants accident and I skipped the winter chapter in between as a flashback scene of some sort. School week starts again with Jian Yi's birthday (Day 5) leading up to the fight with Guan Shan the next day (Day 6). Then He Tian runs into Guan Shan the next day (Day 7) possibly in the morning before school, but He Tian refers to this as another day so also up for interpretation. He Tian and Jian Yi skips school (Day 8), which is also the night when Jian Yi kisses Zheng Xi. They cry and make up, going back to normal the next day (Day 9), which is also the same day Xiao Hui gets humiliated throughout the school and Jian Yi almost gets kidnapped that night!

Shenanigans with the whole lot the next day and we finally learn Hongfa's real name (Day 10) as well as see He Tian steal his (probably) first kiss leading up to a crazy night of Guan Shan deciding to quit school and Jian Yi running around.