When you're 2, a year is 1/2 of your life.

When you're 3, a year is 1/3 of your life.

When you're 30, a year is 1/30th of your life.

Your frame of reference for time is changing every day. Each day feels relatively shorter than the day before.

Strangely though, some years feel very long. To me that's explained by how much activity is going on, day to day. Like how when work is not busy, everyone says "slow day." 2020 for example was less busy for most people (stuck at home), so it was a "slow year."

I dunno, that's my experience anyway.