Defect modes in two-dimensional photonic crystals consisting of nearly-free-electron metals are considered. To avoid any time-consuming time convolution, modified time stepping formulae are used in a finite-difference time-domain (FDTD) method. Compared to the FDTD transmission spectra method, the present method significantly reduces the computation domain. With the present method one can also find defect modes that are not excited by the incident plane wave in the FDTD transmission spectra method.