We present a comprehensive analysis and experimental evaluation of time-based validation techniques for Software Transactional Memory (STM). Time-based validation techniques emerge recently as an effective way to reduce the validation overhead for STM systems. In a time-based strategy, information based on global time enables the system to avoid a full validation pass in many cases where it can quickly prove that no consistency violation is possible given the time information for the current transaction and the object it is attempting to open. We show that none of the current timebased strategies offers the best performance across various applications and thread counts. We also show an adaptive technique which has the potential to achieve an overall best performance based on time information and show some preliminary results we have.