Answer
A year then will feel as 4 months now (1/3 of a year).
Work Step by Step
Let t be perceived time, and a be the age of a person.
t is shorter (less) as a is greater,
t varies inversely as a,$\displaystyle \qquad t=\frac{k}{a}$
If the age a becomes $3a$, the new time perceived, $t_{2}$ is
$t_{2}=\displaystyle \frac{k}{(3a)}=\frac{1}{3}(\frac{k}{a})=\frac{1}{3}t$
(the time perceived then will sem as $\displaystyle \frac{1}{3}$ of time perceived now).
A year then will feel as 4 months now (1/3 of a year).
