Like a day for Nicolas Flamel
Well what do you expect? In 1 year a kid can change drastically, an adult will look relatively the same unless its something extreme like going bald or growing a giant beard.
It's because a year for a five year old represents 1/5 of their life so far. Of course it would feel longer for them. On the other hand a year to a fifty year old feels significantly shorter compared to their lifespan.