However, many programmers began to enable the TZ and DST settings inadvertently when using the “Set Time” button in Controller Properties. In v16 and later this button not only sets the Controller's clock to match the PC's date and time, but also sets the Controller's clock to match the PC's TZ and DST settings. When creating a new program, or importing an older program, the software defaults these new settings to zero which allows programmers to continue to use the “DateTime” attribute as they always had, without any consideration of the new TZ and DST settings. Then in RSLogix 5000 version 16 Rockwell added support for Time Zones (TZ) and Daylight Savings Time (DST,) both of which act as offsets from Coordinated Universal Time (UTC). Note: You can listen to our companion podcast about why your Logix clock may be off a few hours HERE. I found that prior to RSLogix 5000 version 16, using a GSV (“get system variable”) instruction to read the Controller's WallClockTime object's “DateTime” attribute was a popular way to get the actual time into Program or Controller tags. I also found that prior to v16 there had been no support for Time Zones (TZ) or Daylight Savings Time (DST.) ![]() While I had heard this complaint in the past, since I hadn't run into it myself I needed to do a little research to understand what this client was experiencing. ![]() A client recently called frustrated that the real time clock in his CompactLogix processor was always off by 4 hours.
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