The conversion from neutron stars with different equation of states (E
OSs) for neutron matter into strange stars with different EOSs for str
ange quark matter has been studied in a general relativistic numerical
calculation in this paper. For hot neutron stars, their conversion ma
y lead to great variations in their rotation periods, of which the mag
nitude would be greatly dependent upon the EOS for neutron matter, and
of which the timescale would be greatly determined by the EOS for str
ange matter. This phenomenon appears as giant glitches, which might pr
ovide a probe of EOSs far both neutron matter and strange matter. But
for cold neutron stars, their conversion may result in a population of
gamma-ray bursts.