3.4.5 Notes on correcting the system time
Note the following points when you use the NTP program (in Windows, Windows Time service, and in UNIX, commands such as the ntpd command and ntpdate command) to correct the system time. For details on system time correction, see the documentation for the OS in use.
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Use the product in the slew mode range that gradually corrects the shift in time so that the time is not skipped.
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If a large time correction is required, involving several seconds or more at a time, stop the product processes and then correct the time.
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If the system time is turned back or advanced due to the time correction, the following events might occur. Design the system and the timeout considering these events.
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The timeout is delayed or advanced compared to the time assumed for a transaction, communication, and system monitoring
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The log and history time-series collapses
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With some of the component software, if the time is turned back, the operation might become invalid from the point of view of the function properties.