From 0e3a3bd2c722ae1aea3fd106e23b07bd0bcba929 Mon Sep 17 00:00:00 2001
From: AKIBUZZAMAN AKIB <akibuzzaman@users.noreply.github.com>
Date: Thu, 30 Apr 2026 23:03:44 +0000
Subject: [PATCH] fix(time-scale): getLabelForValue uses current unit
 displayFormat

Previously, getLabelForValue() always fell back to the 'datetime'
displayFormat regardless of the current time unit. This caused
inconsistency when a custom displayFormat was set for the active
unit (e.g. unit: 'month', displayFormats: { month: 'MMM YYYY' }),
because the tooltip label would show the full datetime format instead.

The format() method on the same scale correctly uses this._unit to
pick the right displayFormat, so getLabelForValue() should do the same.

Fix by using displayFormats[this._unit] with a fallback to 'datetime'
when no unit-specific format is defined.

Fixes #12128
---
 src/scales/scale.time.js       |  2 +-
 test/specs/scale.time.tests.js | 36 ++++++++++++++++++++++++++++++++++
 2 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/src/scales/scale.time.js b/src/scales/scale.time.js
index f82d43ad72d..55823186f3e 100644
--- a/src/scales/scale.time.js
+++ b/src/scales/scale.time.js
@@ -499,7 +499,7 @@ export default class TimeScale extends Scale {
     if (timeOpts.tooltipFormat) {
       return adapter.format(value, timeOpts.tooltipFormat);
     }
-    return adapter.format(value, timeOpts.displayFormats.datetime);
+    return adapter.format(value, timeOpts.displayFormats[this._unit] || timeOpts.displayFormats.datetime);
   }
 
   /**
diff --git a/test/specs/scale.time.tests.js b/test/specs/scale.time.tests.js
index 42817ae15c9..f566a9c8fcf 100644
--- a/test/specs/scale.time.tests.js
+++ b/test/specs/scale.time.tests.js
@@ -456,6 +456,42 @@ describe('Time scale tests', function() {
     }
   });
 
+  it('getLabelForValue should use the current unit displayFormat, not datetime (issue #12128)', function() {
+    var chart = window.acquireChart({
+      type: 'line',
+      data: {
+        datasets: [{
+          xAxisID: 'x',
+          data: [
+            {x: '2015-01-01', y: 10},
+            {x: '2015-02-01', y: 20},
+            {x: '2015-03-01', y: 30}
+          ]
+        }]
+      },
+      options: {
+        scales: {
+          x: {
+            type: 'time',
+            time: {
+              unit: 'month',
+              displayFormats: {
+                month: 'MMM YYYY'
+              }
+            }
+          }
+        }
+      }
+    });
+
+    var xScale = chart.scales.x;
+    var controller = chart.getDatasetMeta(0).controller;
+    var value = controller.getParsed(0)[xScale.id];
+
+    // Should use 'month' displayFormat ('MMM YYYY'), not 'datetime'
+    expect(xScale.getLabelForValue(value)).toBe('Jan 2015');
+  });
+
   it('should round to isoWeekday', function() {
     var chart = window.acquireChart({
       type: 'line',