Adding fix for issue 6661

Author: 28raining

src/traces/histogram/calc.js

@@ -309,7 +309,8 @@ function calcAllAutoBins(gd, trace, pa, mainData, _overlayEdgeCase) {
         // Edge case: single-valued histogram overlaying others
         // Use them all together to calculate the bin size for the single-valued one
         if(isOverlay && !Registry.traceIs(trace, '2dMap') && newBinSpec._dataSpan === 0 &&
-            pa.type !== 'category' && pa.type !== 'multicategory') {
+        pa.type !== 'category' && pa.type !== 'multicategory' &&
+        trace.bingroup !== '' && (typeof trace.xbins !== 'undefined')) {
             // Several single-valued histograms! Stop infinite recursion,
             // just return an extra flag that tells handleSingleValueOverlays
             // to sort out this trace too

test/image/baselines/histogram_overlay-1point-date.png

@@ -0,0 +1,48 @@
+{
+  "data": [
+    {
+      "x": ["2023-05-22 09:29:56.00"],
+      "opacity": 1,
+      "type": "histogram",
+      "name": "Results B",
+      "marker": {
+        "color": "rgba(0, 255, 0, .2)",
+        "line": {
+          "color": "rgba(0, 255, 0, 1)",
+          "width": 2
+        }
+      },
+      "xbins": {
+        "size": "M1",
+        "start": "2023-05-01",
+        "end": "2023-07-01"
+      }
+    },
+    {
+      "x": ["2023-05-21 09:29:56.00", "2023-05-26 09:29:56.00", "2023-06-21 09:29:56.00"],
+      "opacity": 1,
+      "type": "histogram",
+      "name": "Results A",
+      "marker": {
+        "color": "rgba(0, 0, 255, .2)",
+        "line": {
+          "color": "rgba(0, 0, 255, 1)",
+          "width": 2
+        }
+      },
+      "xbins": {
+        "size": "M1",
+        "start": "2023-05-01",
+        "end": "2023-07-01"
+      }
+    }
+  ],
+  "layout": {
+    "barmode": "overlay",
+    "title": "Sampled Results",
+    "xaxis": {
+      "title": "Date"
+    },
+    "yaxis": { "title": "Count" }
+  }
+}