I know Americans do that
I never understood it. I need the time to get used to my new age, so I start around January, which gives me about 4 months and also it makes sense with the counting of the years. Anyway, the one year when I didn't do it was when I was living in the US. I said I was 26 to the last days and the only time I didn't I almost got into trouble (because the travelling fees I had to pay as a 26-year-old were cheaper).
