The internal computer clocks is not very accurate. The deviation is especially noticeable over extended periods of time. You can synchronize your computer clock over the Internet with one of several atomic clocks in the country. The 4dtime utility from Thinking Man synchronizes your computer's clock on a regular basis. It can be downloaded from www.thinkman.com. The dialog to select the atomic clock server and to select the update frequency is shown in the next figure.
Figure 41. 4dTime Computer Clock Synchronization Utility