src/components/EventOverlay.vue

@@ -101,6 +101,24 @@ function handleEventPointerDown(span, event) {
   const hasVirtualMarker = typeof idStr === 'string' && idStr.includes('_v_')
   const baseId = hasVirtualMarker ? idStr.slice(0, idStr.lastIndexOf('_v_')) : idStr
   const isVirtual = hasVirtualMarker
+  // Determine which day within the span was grabbed so we maintain relative position
+  let anchorDate = span.startDate
+  try {
+    const spanDays = daysInclusive(span.startDate, span.endDate)
+    const targetEl = event.currentTarget
+    if (targetEl && spanDays > 0) {
+      const rect = targetEl.getBoundingClientRect()
+      const relX = event.clientX - rect.left
+      const dayWidth = rect.width / spanDays
+      let dayIndex = Math.floor(relX / dayWidth)
+      if (!isFinite(dayIndex)) dayIndex = 0
+      if (dayIndex < 0) dayIndex = 0
+      if (dayIndex >= spanDays) dayIndex = spanDays - 1
+      anchorDate = addDaysStr(span.startDate, dayIndex)
+    }
+  } catch (e) {
+    // Fallback to startDate if any calculation fails
+  }
   startLocalDrag(
     {
       id: baseId,
@@ -109,7 +127,7 @@ function handleEventPointerDown(span, event) {
       mode: 'move',
       pointerStartX: event.clientX,
       pointerStartY: event.clientY,
-      anchorDate: span.startDate,
+      anchorDate,
       startDate: span.startDate,
       endDate: span.endDate,
     },