  We have investigated an approach to determine the Majorana type-phases using
the time evolution of lepton family numbers. The Majorana type-phases are
related to the orientation of unitarity triangles for the
Pontecorvo-Maki-Nakagawa-Sakata (PMNS) matrix, and the Majorana phases
$\alpha_{21}$ and $\alpha_{31}$. After taking the second-order time derivative
of the lepton family number expectation values, the dependencies on the
summation of Majorana type-phases can be determined. Thus allowing for the
extraction of the orientation of the unitarity triangles and the Majorana
phases. We study how to extract the Majorana type-phases and the lightest
neutrino mass for three massive neutrinos, and when a neutrino is massless,
i.e., $m_{1,3}=0$. Our result can be complimentary to using neutrinoless
double-beta decay for determining the orientation of PMNS unitarity triangles
and the Majorana phases.
