You are programming a SIEMENS S7 1500 or S7 1200 PLC and wondering what is the difference between local and system time? Or having troubles setting the PLC time. In this article you will find simple explanation of the two functions and how to set the time properly.
First let us see what is the difference between “system time” & “local time”.
System time
The “system time” is the global time UTC±00:00.
Local time
The “local time” refers to the local time in means of where the CPU is operating. For example, it may be in Germany UTC +1.
To set the global time go to “Device configuration” (Image 1) and the in “Time of day” (Image 2) the time zone can be chosen. Respectively the “daylight saving time” can be activated.
Image 1. Device configuration
Image 2 Time of day
Function blocks
There are function blocks in the TIA library, which allow reading and writing from/to the system and the local time.
Image 3 Date and time function blocks
