This paper presents a nonorthogonal finite-difference time-domain (NFDTD) modelling of photonic bandgap (PBG) structures. The NFDTD method discretises the curved structures in a conformal way. As a result, when the curved elements or oblique surfaces are involved in the EBG structure, the NFDTD scheme requires much fewer cells compared with the conventional Yees scheme. Consequently the requirement of the computer memory and the computation time can be reduced.