The brain is very good at compressing information, so if your days are fairly similar to each other they'll all blur together. And I don't mean the things you think about, but the places you go to. Real places, I might add.
If you rarely discover real places you've never been to, the memory will just be compressed and it seems like last year that you moved from your last place, when it was actually forty years ago.
Now, this can be alleviated by instead of visiting new places learning new things, but those things have to be actually new to your brain and not just more of something you are already familiar with. Otherwise it gets compressed all the same.
New places, new things, new people, new routines all reset the clock.
Subjectively it felt like I lived about 5 years in the first 2 months after my first kid was born - certainly they were more memorable than the previous 5 years. We were basically confined to the apartment except for doctor's visits during that time period, but the experience of caring for a little person was dramatically different from everything that came before. And then the newborn periods of our 2nd and 3rd kids flew by, because we had all the routines down.
2020 also felt like I lived a lifetime in a year, even though we were shut-in, because of all the events and changes of routine that year.