The main function of timestamp system is to synchronize the clock of control computers in the control system of an accelerator.Through timestamp system

one can make sure the precise causality between all kinds of data for trouble shooting and data analysis.In this paper

we describe the principle of timestamp system

and analyze the hardware structure and realization mechanism between several large accelerators in detail.A design of timestamp systems for lab environment is presented for applications at SSRF.Finally

we summarize the difference between these timestamp systems.