Structured Text - Need to Subtract 1y from DT in ST Logic

[kvacola]

[Using ClearSCADA 2017 R3]

I have a structured text program that is calculating a date and time from 2 FloBoss integers. INT1 is the Date (without year) and is a 4-digit value (e.g. 0226). INT2 is the 4-digit Time in 24h format (e.g. 1442). I've successfully gotten to the point in my ST program where I have the date. Unfortunately for dates that straddle the year for this device, I need to be able to subtract 1 year from the date. I use the current date and time to extract 'YEAR' and do a couple of concatenations to get the time:

dtDate		:= MAKE_DATE(YEAR, STRING_TO_SINT(strMonth), STRING_TO_SINT(strDay));
dtTime		:= MAKE_TIME_OF_DAY(STRING_TO_SINT(strHour), STRING_TO_SINT(strMins), 0, 0);	
DATETIME	:= CONCAT_D_TOD(dtDate, dtTime);

But the final function that compares the current time to the calculated time is giving me the error 'Program Error: Invalid conversion'

IF DATETIME > dtCurrentTime THEN
	DATETIME	:= SUB_DT_TIME(DATETIME, STRING_TO_TIME('D#1y'));
END_IF;

The program compiles just fine, I only get the error when I execute the program.

[BevanWeiss]

If these are all INTs... why are you doing anything with STRINGs?

CURR_INT1 := EXTRACT_DT_MONTH(NOW()) * 100 + EXTRACT_DT_DAY(NOW());

CURR_INT2 := EXTRACT_DT_HOUR(NOW()) *100 + EXTRACT_DT_MINUTE(NOW());



IF( CURR_INT1 > INT1 OR (CURR_INT1 = INT1 AND CURR_INT2 >= INT2)) THEN

    (* Our datetime event was this year.. *)

    (* We don't care about Seconds / Milliseconds, so set these to zero *)

    (* INT1 = MMDD, INT2 = HHMM *)

    DATETIME := MAKE_DATE_AND_TIME( YEAR, DIV( INT1, 100), MOD(INT1,100), DIV(INT2,100), MOD(INT2,100), 0, 0 );

ELSE

  (* our datetime event was last year *)

    (* We don't care about Seconds / Milliseconds, so set these to zero *)

    (* INT1 = MMDD, INT2 = HHMM *)

    DATETIME := MAKE_DATE_AND_TIME( YEAR - 1, DIV( INT1, 100), MOD(INT1,100), DIV(INT2,100), MOD(INT2,100), 0, 0 );



END_IF;

[kvacola]

That did the trick! Thanks so much. I though I'd have to convert to strings to parse off the month/day and hour/min.

[AdamWoodland · Accepted solution]

Might have been able to get away with:

DATETIME := SUB_DT_TIME(DATETIME, T#365d);

Although would need to take leap years into account.

[BevanWeiss]

@kvacola How did you get somewhat good syntax colouring on your ST Logic text?  Did you have to colour it yourself?

@AdamWoodland It is a little frustrating that the logic engine (and many parts of ClearSCADA) can't do subtraction of things like months / years etc (conceptual time periods).  I was a bit afraid that 1year in days would overflow the holding of the 'Time' datatype.  What is the extent of what it can hold?

[sbeadle]

That was 'C' language colouring. Colours function names red but is unaware of  (* *) comments.

Time and its text representations support, for example, a century's worth of seconds in Adam's example.