start 1.5 * 28 in the past

src/main.ts

@@ -186,15 +186,15 @@ function renderCharts(activities: Activity[], targetAcwr: number): void {
     // Calculate date range from first activity to today
     let dateRange: { start: Date; end: Date } | undefined;
     if (allActivities.length > 0) {
-        const sortedAll = [...allActivities].sort((a, b) => a.date.getTime() - b.date.getTime());
-        // Normalize to midnight to avoid timezone/time comparison issues
-        const startDate = new Date(sortedAll[0].date);
-        startDate.setHours(0, 0, 0, 0);
-        
         // Use current date/time as end date (today)
         const endDate = new Date();
         endDate.setHours(23, 59, 59, 999);
-        
+
+        // Calculate start date as 1.5 times chronic workload period (28 days) before today
+        const startDate = new Date(endDate);
+        startDate.setDate(startDate.getDate() - Math.floor(28 * 1.5));
+        startDate.setHours(0, 0, 0, 0);
+
         dateRange = {
             start: startDate,
             end: endDate,