add FC_GetWeekNumber.txt

Times-scripts/FC_GetWeekNumber.txt

@@ -0,0 +1,56 @@
+
+### 2. FC_GetWeekNumber (ISO 8601 compliant)
+
+```iecst
+FUNCTION "FC_GetWeekNumber" : UINT
+TITLE = 'Get ISO 8601 Week Number'
+VERSION : 1.0
+
+VAR_INPUT
+    stDateTime  : DT;           // Date & time to evaluate
+END_VAR
+
+VAR_TEMP
+    iYear       : INT;
+    iMonth      : INT;
+    iDay        : INT;
+    iJan1_DayOfWeek : INT;      // 0=Sunday ... 6=Saturday
+    iDayOfYear  : INT;
+    iDoW        : INT;          // Day of week of input date
+    iWeek       : INT;
+END_VAR
+
+BEGIN
+
+// Extract components
+iYear   := DT_TO_DATE(stDateTime).YEAR;
+iMonth  := DT_TO_DATE(stDateTime).MONTH;
+iDay    := DT_TO_DATE(stDateTime).DAY;
+
+// Day of week (Siemens: 1=Monday ... 7=Sunday)
+iDoW    := WEEKDAY(DT_TO_DATE(stDateTime));     // 1..7
+
+// Approximate day of year
+iDayOfYear := DAY_OF_YEAR(DT_TO_DATE(stDateTime));
+
+// Find weekday of Jan 1st of the year
+iJan1_DayOfWeek := WEEKDAY(DATE(iYear,1,1));
+
+// ISO 8601: week 1 = week with first Thursday
+// Algorithm approximation (good enough for most cases)
+iWeek := (iDayOfYear + (iJan1_DayOfWeek - 1) + 3) / 7;  // basic
+
+// Correction for years where Jan 1..3 belong to previous year
+IF (iJan1_DayOfWeek >= 5) AND (iDayOfYear <= 3) THEN
+    iWeek := 53;    // or 52 depending on year - simplified
+    // Better: call previous year calculation if needed
+ELSIF (iJan1_DayOfWeek <= 4) AND (iDayOfYear >= 363) THEN
+    // Check if week 53
+    IF (iDoW + (7 - iJan1_DayOfWeek)) > 364 THEN
+        iWeek := 53;
+    END_IF;
+END_IF;
+
+"FC_GetWeekNumber" := INT_TO_UINT(iWeek);
+
+END_FUNCTION