For orthogonal frequency division multiplexing (OFDM) based indoor visible light communication (VLC) systems, we show that the subcarrier channels tend to synchronize and add up to a resultant high peak signal at the leading edge of each symbol when using certain types of modulation formats. Thus, occasional non-ideal transmission conditions such as insufficient guard intervals and a dispersive channel will result in inter-symbol crosstalk. This paper presents a time domain reshuffling (TDR) technique for both DC-biased optical (DCO-) and asymmetrically clipped optical (ACO-) OFDM based VLC systems. Only by simple operations in the frequency domain, the potential high peaks can be relocated in each OFDM symbol to alleviate the crosstalk. Based on Monte-Carlo simulations, we demonstrate the statistical distribution of the signal high peak values and the complementary cumulative distribution function of the peak-to-average power ratio for comparison. By adopting the TDR method, we show that the bit error rate performance can be also improved for both DCO- and ACO-OFDM systems under occasional non-ideal transmission conditions.