One has studied time-dependent changes of morphological properties of uniaxial lyotropic nematic-calamitic NC and nematic- discotic ND mesophases with various external magnetic field values. Also, changes of optical birefringence values of NC and ND lyotropic mesophases under influence of the magnetic fields has been investigated based on time. Differences of morphological properties and changing birefringence values between NC and ND mesophases have been interpreted according to magnetic field values. The values of optical birefringence and morphological properties changing in time between NC and ND mesophases which are opposite signs of diamagnetic anisotropy have been compared with increasing magnetic field values.