Applying Daylight Savings Time

When migrating alarms or Classic Historian data, you can select whether or not you want to apply Daylight Savings Time (DST) bias to timestamps. The Migration Utility converts the timestamps of migrated samples to UTC time (universal time format for storing timestamps) before writing the data to Historian. If you select this option, the Migration Utility will apply the DST offset before converting to UTC time. The timestamps are converted to UTC time by adjusting the time based on the local computer time zone offset and DST setting.

If you enabled DST in your operating system during data or alarm logging, you must select the Treat as DST Timestamp option. With Classic Historian, a switch from Daylight Time to Standard Time results in a loss of one hour of data between 1:00:00 and 1:59:59 AM. With Historian, no loss of data occurs when you switch from Daylight Time to Standard Time.

Note: The migration utilities assume that the computer you are migrating your data from and the computer that you are migrating your data to are in the same Time Zone.