Hah. The ‘legal quirk’ is that there is no age limit to run for this office.
From his website, which is linked to in another comment:
Is This Legal?
Yes! According to the Vermont Constitution and the Vermont Attorney General, you only have to have lived in Vermont for 4 years or more on the day before the election. Ethan has lived here for 14 years.
It would 3 years and 3.25 months if you want to actually be accurate.