Siemens SIMATIC S7-200 System Manual page 260

SIMATIC Instructions
The time-of-day clock initializes the following date and time after extended power
outages or memory has been lost:
Date:
Time:
Day of Week
The time-of-day clock in the S7-200 uses only the least significant two digits for the
year, so for the year 2000, the year is represented as 00.
You must code all date and time values in BCD format (for example, 16#97 for the
year 1997). Use the following data formats:
Year/Month
Day/Hour
Minute/Second mmss
Day of week
Note
The S7-200 CPU does not perform a check to verify that the day of week is
correct based upon the date. Invalid dates, such as February 30, may be
accepted. You should ensure that the date you enter is correct.
Do not use the TODR/TODW instruction in both the main program and in an
interrupt routine. A TODR/TODW instruction in an interrupt routine which attempts
to execute while another TODR/TODW instruction is in process will not be
executed. SM4.3 is set indicating that two simultaneous accesses to the clock
were attempted (non-fatal error 0007).
The S7-200 PLC does not use the year information in any way and is not affected
by the century rollover (year 2000). However, user programs that use arithmetic or
compares with the year's value must take into account the two-digit representation
and the change in century.
Leap year is correctly handled through year 2096.
9-72
01-Jan-90
00:00:00
Sunday
yymm yy - 0 to 99
ddhh dd - 1 to 31
mm - 0 to 59
d d - 0 to 7
mm - 1 to 12
hh - 0 to 23
ss - 0 to 59
1 = Sunday
0 = disables day of week
(remains 0)
S7-200 Programmable Controller System Manual
A5E00066097-02