The title "Groundhog Day" is taken from the movie of the same name.
It represents an inexplicable repetition of time. People trapped in it will live a certain day over and over again, meet the same people, and have the same events happen.
His time is stuck on this day forever.
And this day after day will be endless.
To put it figuratively, it's like starting a chapter and saving it when playing a game, except that no matter what the person trapped in it does, the ending will always be game over, and then start over from the beginning of this chapter.
No matter what you change today, it will only exist in your memory. When you wake up the next day, everything will be zero.
I thought I could change everything, thought I could save everything, but when I woke up again, everything was back to where it started.
PS: Xiaomao Runcheng, Saving Jinjian [=w=], related to episodes 18~20 of the CH TV series.
PPS: I watched episode 19 [that is, the TvT episode with Jin Jian Ling Bento] seriously over and over again. Except for the last part, it was never dark ╮(╯_╰)╭, so I generously treated those events as happening on the same day, so that the plot can be developed~