There's some solid advice in the article. However, childhood summers don't seem long primarily because you're doing new things, but rather because of relative perception of time. When you're two years old, one summer spans 1/8 of your life. Unless you live in the UK.
Can you link to something where this scientific concept is from? I've only ever seen this in the cute not scientific video linked elsewhere here, and have taken it as false. A nice cute plot for a story but not true. I'd be interested to see something backing it up.
Unfortunately I can't. It's not a scientific concept, just something that seems intuitively correct to me (haven't seen the video before, came up with the same concept independently, as I imagine many others did). Could you try to explain why you consider it false?
The only thing I can back it up with is a personal anecdote - when I was five, twenty minutes in a tram seemed like ages, despite having taken that same ride many times.