Figure 74
The Date/Time tab lets you set the appliance system time so that the time stamps in cache logs are accurate and valid. An ISP, for example, might bill customers based on their access to the appliance. Accurate log time stamps are essential to issuing credible billing statements.
NOTE: Excelerator stamps log entries with Greenwich Mean Time (GMT). If the appliance is using an NTP server, the GMT stamp comes from that server. If the appliance is using a manually set time, Excelerator assumes the time is accurate and calculates the GMT value based on the appliance's time zone and daylight saving settings.
Use Network Time Protocol: Checking this option turns network time protocol on or off. This enables the appliance to synchronize its system time with an NTP server. Using an NTP server makes appliance cache log time stamps as reliable as possible. This can be especially important if you use the logs for customer billing. The appliance comes with two sample NTP servers: 132.163.4.101 and 132.163.4.103. You can remove these or add other NTP servers.
IMPORTANT: When you specify an NTP server, synchronization between the NTP server clock and the appliance clock might not be immediate.
If the NTP server clock has an earlier time than the appliance clock, Excelerator will slow down the appliance clock until the two are synchronized. This provides for proper incrementation of log files and other time-sensitive information during the synchronization process.
If the NTP server clock has a later time setting than the appliance clock, synchronization between the two will generally be immediate. However, in certain situations you might observe the appliance clock incrementing by 600-minute intervals. This is normal system behavior.
The Apply button changes from Wait back to Apply. This indicates only that the NTP configuration change has been made, not that the appliance clock is fully synchronized with the NTP server.
If necessary, you can set appliance time manually to the target time and then re-enable the NTP feature.
Set Date/Time Manually: The dialog box in Figure 75 appears when you select this button and click Set Time. Set the date and time using the drop-down lists. Clicking OK immediately resets the system clock.
Figure 75 
Use this option if NTP is not available to your appliance or if you need to set a specific time.