diff --git a/src/agenda/AgendaEventRenderer.js b/src/agenda/AgendaEventRenderer.js
index 62e4143..6a51306 100644
--- a/src/agenda/AgendaEventRenderer.js
+++ b/src/agenda/AgendaEventRenderer.js
@@ -26,6 +26,7 @@ function AgendaEventRenderer() {
 	var getMaxMinute = t.getMaxMinute;
 	var getMinMinute = t.getMinMinute;
 	var timePosition = t.timePosition;
+	var getIsCellAllDay = t.getIsCellAllDay;
 	var colContentLeft = t.colContentLeft;
 	var colContentRight = t.colContentRight;
 	var cellToDate = t.cellToDate;
@@ -472,80 +473,148 @@ function AgendaEventRenderer() {
 	// when event starts out IN TIMESLOTS
 	
 	function draggableSlotEvent(event, eventElement, timeElement) {
-		var origPosition;
-		var allDay = false;
-		var dayDelta;
-		var minuteDelta;
-		var prevMinuteDelta;
-		var hoverListener = getHoverListener();
+		var coordinateGrid = t.getCoordinateGrid();
 		var colCnt = getColCnt();
 		var colWidth = getColWidth();
 		var snapHeight = getSnapHeight();
 		var snapMinutes = getSnapMinutes();
+
+		// states
+		var origPosition; // original position of the element, not the mouse
+		var origCell;
+		var isInBounds, prevIsInBounds;
+		var isAllDay, prevIsAllDay;
+		var colDelta, prevColDelta;
+		var dayDelta; // derived from colDelta
+		var minuteDelta, prevMinuteDelta;
+
 		eventElement.draggable({
 			zIndex: 9,
 			scroll: false,
-			grid: [colWidth, snapHeight],
+			grid: [ colWidth, snapHeight ],
 			axis: colCnt==1 ? 'y' : false,
 			opacity: opt('dragOpacity'),
 			revertDuration: opt('dragRevertDuration'),
 			start: function(ev, ui) {
+
 				trigger('eventDragStart', eventElement, event, ev, ui);
 				hideEvents(event, eventElement);
+
+				coordinateGrid.build();
+
+				// initialize states
 				origPosition = eventElement.position();
+				origCell = coordinateGrid.cell(ev.pageX, ev.pageY);
+				isInBounds = prevIsInBounds = true;
+				isAllDay = prevIsAllDay = getIsCellAllDay(origCell);
+				colDelta = prevColDelta = 0;
+				dayDelta = 0;
 				minuteDelta = prevMinuteDelta = 0;
-				hoverListener.start(function(cell, origCell) {
-					eventElement.draggable('option', 'revert', !cell);
-					clearOverlays();
-					if (cell) {
-						var origDate = cellToDate(0, origCell.col);
-						var date = cellToDate(0, cell.col);
-						dayDelta = dayDiff(date, origDate);
-						if (opt('allDaySlot') && !cell.row) {
-							// over full days
-							if (!allDay) {
-								// convert to temporary all-day event
-								allDay = true;
-								timeElement.hide();
-								eventElement.draggable('option', 'grid', null);
-							}
-							renderDayOverlay(
-								addDays(cloneDate(event.start), dayDelta),
-								addDays(exclEndDay(event), dayDelta)
-							);
-						}else{
-							// on slots
-							resetElement();
-						}
-					}
-				}, ev, 'drag');
+
 			},
 			drag: function(ev, ui) {
-				minuteDelta = Math.round((ui.position.top - origPosition.top) / snapHeight) * snapMinutes;
-				if (minuteDelta != prevMinuteDelta) {
-					if (!allDay) {
-						updateTimeText(minuteDelta);
+
+				// NOTE: this `cell` value is only useful for determining in-bounds and all-day.
+				// Bad for anything else due to the discrepancy between the mouse position and the
+				// element position while snapping. (problem revealed in PR #55)
+				//
+				// PS- the problem exists for draggableDayEvent() when dragging an all-day event to a slot event.
+				// We should overhaul the dragging system and stop relying on jQuery UI.
+				var cell = coordinateGrid.cell(ev.pageX, ev.pageY);
+
+				// update states
+				isInBounds = !!cell;
+				if (isInBounds) {
+					isAllDay = getIsCellAllDay(cell);
+
+					// calculate column delta
+					colDelta = Math.round((ui.position.left - origPosition.left) / colWidth);
+					if (colDelta != prevColDelta) {
+						// calculate the day delta based off of the original clicked column and the column delta
+						var origDate = cellToDate(0, origCell.col);
+						var col = origCell.col + colDelta;
+						col = Math.max(0, col);
+						col = Math.min(colCnt-1, col);
+						var date = cellToDate(0, col);
+						dayDelta = dayDiff(date, origDate);
 					}
+
+					// calculate minute delta (only if over slots)
+					if (!isAllDay) {
+						minuteDelta = Math.round((ui.position.top - origPosition.top) / snapHeight) * snapMinutes;
+					}
+				}
+
+				// any state changes?
+				if (
+					isInBounds != prevIsInBounds ||
+					isAllDay != prevIsAllDay ||
+					colDelta != prevColDelta ||
+					minuteDelta != prevMinuteDelta
+				) {
+
+					updateUI();
+
+					// update previous states for next time
+					prevIsInBounds = isInBounds;
+					prevIsAllDay = isAllDay;
+					prevColDelta = colDelta;
 					prevMinuteDelta = minuteDelta;
 				}
+
+				// if out-of-bounds, revert when done, and vice versa.
+				eventElement.draggable('option', 'revert', !isInBounds);
+
 			},
 			stop: function(ev, ui) {
-				var cell = hoverListener.stop();
+
 				clearOverlays();
 				trigger('eventDragStop', eventElement, event, ev, ui);
-				if (cell && (dayDelta || minuteDelta || allDay)) {
-					// changed!
-					eventDrop(this, event, dayDelta, allDay ? 0 : minuteDelta, allDay, ev, ui);
-				}else{
-					// either no change or out-of-bounds (draggable has already reverted)
-					resetElement();
+
+				if (isInBounds && (isAllDay || dayDelta || minuteDelta)) { // changed!
+					eventDrop(this, event, dayDelta, isAllDay ? 0 : minuteDelta, isAllDay, ev, ui);
+				}
+				else { // either no change or out-of-bounds (draggable has already reverted)
+
+					// reset states for next time, and for updateUI()
+					isInBounds = true;
+					isAllDay = false;
+					colDelta = 0;
+					dayDelta = 0;
+					minuteDelta = 0;
+
+					updateUI();
 					eventElement.css('filter', ''); // clear IE opacity side-effects
-					eventElement.css(origPosition); // sometimes fast drags make event revert to wrong position
-					updateTimeText(0);
+
+					// sometimes fast drags make event revert to wrong position, so reset.
+					// also, if we dragged the element out of the area because of snapping,
+					// but the *mouse* is still in bounds, we need to reset the position.
+					eventElement.css(origPosition);
+
 					showEvents(event, eventElement);
 				}
 			}
 		});
+
+		function updateUI() {
+			clearOverlays();
+			if (isInBounds) {
+				if (isAllDay) {
+					timeElement.hide();
+					eventElement.draggable('option', 'grid', null); // disable grid snapping
+					renderDayOverlay(
+						addDays(cloneDate(event.start), dayDelta),
+						addDays(exclEndDay(event), dayDelta)
+					);
+				}
+				else {
+					updateTimeText(minuteDelta);
+					timeElement.css('display', ''); // show() was causing display=inline
+					eventElement.draggable('option', 'grid', [colWidth, snapHeight]); // re-enable grid snapping
+				}
+			}
+		}
+
 		function updateTimeText(minuteDelta) {
 			var newStart = addMinutes(cloneDate(event.start), minuteDelta);
 			var newEnd;
@@ -554,14 +623,7 @@ function AgendaEventRenderer() {
 			}
 			timeElement.text(formatDates(newStart, newEnd, opt('timeFormat')));
 		}
-		function resetElement() {
-			// convert back to original slot-event
-			if (allDay) {
-				timeElement.css('display', ''); // show() was causing display=inline
-				eventElement.draggable('option', 'grid', [colWidth, snapHeight]);
-				allDay = false;
-			}
-		}
+
 	}
 	
 	
diff --git a/src/agenda/AgendaView.js b/src/agenda/AgendaView.js
index d8d0f1f..a237556 100644
--- a/src/agenda/AgendaView.js
+++ b/src/agenda/AgendaView.js
@@ -35,6 +35,7 @@ function AgendaView(element, calendar, viewName) {
 	t.timePosition = timePosition;
 	t.getIsCellAllDay = getIsCellAllDay;
 	t.allDayRow = getAllDayRow;
+	t.getCoordinateGrid = function() { return coordinateGrid }; // specifically for AgendaEventRenderer
 	t.getHoverListener = function() { return hoverListener };
 	t.colLeft = colLeft;
 	t.colRight = colRight;