= Solution
Equating the lander and return-signal positions gives
$$
\frac{35}{37}t_D=2-\left(t_D-\frac{25}{12}\right),\qquad\boxed{t_D=\frac{1813}{864}\,\mathrm{yr}=2.09838\,\mathrm{yr}.}
$$
This is measured from launch, so about 25.18 months pass on Earth-frame synchronized clocks. D occurs slightly before the lander reaches Earth at $t=74/35\,\mathrm{yr}$.
The two events A and D lie on the inertial lander's own <worldline>, and their <proper time> difference is
$$
\boxed{\Delta\tau=\frac{t_D}{\gamma_u}=\frac{49}{72}\,\mathrm{yr}=0.68056\,\mathrm{yr}\simeq8.17\text{ months}.}
$$
Equivalently, applying the <Lorentz transformation> with $\Delta x=u\Delta t$ gives $\Delta t'=\gamma_u\Delta t(1-u^2/c^2)=\Delta t/\gamma_u$.
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