This sounds like a reasonable argument, but I don't think it is. A day for a 4 year old still takes the same 24 hours as a day for a 40 year old.
The argument presupposes that you experience the length of an event relative to the sum length of all experiences you've lived through. That seems pretty much related to the premise of the article we are discussing. So it's not much simpler.
Comparatively, that difference is huge: a year is far more significant to the child than to the adult.