Tagmentation-based methylation sequencing (TIME-seq) is an efficient and cost-effective solution for measuring and generating epigenetic clocks. We applied TIME-seq to over 2,800 mouse and human DNA samples to produce clocks that demonstrate accuracy and robustness; the method also outperforms conventional methods in speed and cost. The simple and practical design of TIME-seq facilitates large-scale epigenetic clock analysis, which makes it a valuable tool for advancing aging research.