Technical data

Establishing an Online Connection and Making CPU Settings
18.3 Displaying and Setting the Time and Date
Programming with STEP 7
Manual, 05/2010, A5E02789666-01 409
18.3 Displaying and Setting the Time and Date
18.3.1 CPU Clocks with Time Zone Setting and Summer/Winter Time
On S7-400 CPUs as of firmware version 3, you can make or evaluate the following settings in
addition to the time and date:
• Summer/Winter Time
• Offset factors for displaying time zones
Display of Time Zones
The system operates with a TOD that is global, continuous and free of interrupts, namely the
Module Time.
The local automation system allows the calculation of a Local Time that differs from Module Time
and which can be used by the user program. Local Time is not entered directly, but is rather
calculated using the Module Time plus/minus a time difference to Module Time).
Summer/Winter Time
You can also set daylight-saving or standard time when you set up the TOD and the date. When
switching from daylight-saving to standard time, for example, per user program only the time
difference to the Module Time is taken into account. You can make this changeover with a block
made available to you via the Internet.
Reading and Adjusting the TOD and The TOD Status
The summer/winter time identifier and time difference to the Module Time are included in the
Time-Of-Day (TOD) status.
You have the following options to read or adjust the TOD and its status:
With STEP 7 (online)
• Via menu command PLC > Diagnostics/Setting > Adjust TOD (read and adjust)
• Via the "Module Information" dialog box, "Time System" tab (read only)
In the user program
• SFC 100 "SET_CLKS" (read and adjust)
• SFC 51 "RDSYSST" with SZL 132, Index 8 (read only)
Time Stamp in the Diagnostic Buffer, Messages and OB-Start Information
Time stamps are generated using the Module Time.