From bfa0eefa32a46628d97a4f5bc3f86e9d07764a53 Mon Sep 17 00:00:00 2001
From: darshanr0107 <darshan@mermaid.com>
Date: Fri, 27 Jun 2025 15:01:45 +0530
Subject: [PATCH] fix gantt chart date format issue

---
 cypress/integration/rendering/gantt.spec.js       | 12 ++++++++++++
 .../mermaid/src/diagrams/gantt/ganttRenderer.js   | 15 +++++++++++++--
 2 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/cypress/integration/rendering/gantt.spec.js b/cypress/integration/rendering/gantt.spec.js
index 2cc67918c..fed4151ec 100644
--- a/cypress/integration/rendering/gantt.spec.js
+++ b/cypress/integration/rendering/gantt.spec.js
@@ -565,6 +565,18 @@ describe('Gantt diagram', () => {
     );
   });
 
+  it('should render only the day when using dateFormat D', () => {
+    imgSnapshotTest(
+      `
+    gantt
+      title Test
+      dateFormat D
+      A :a, 1, 1d
+    `,
+      {}
+    );
+  });
+
   // TODO: fix it
   //
   // This test is skipped deliberately
diff --git a/packages/mermaid/src/diagrams/gantt/ganttRenderer.js b/packages/mermaid/src/diagrams/gantt/ganttRenderer.js
index f5c8c2e38..66ada61c8 100644
--- a/packages/mermaid/src/diagrams/gantt/ganttRenderer.js
+++ b/packages/mermaid/src/diagrams/gantt/ganttRenderer.js
@@ -615,9 +615,20 @@ export const draw = function (text, id, version, diagObj) {
    * @param h
    */
   function makeGrid(theSidePad, theTopPad, w, h) {
+    const dateFormat = diagObj.db.getDateFormat();
+    const userAxisFormat = diagObj.db.getAxisFormat();
+    let axisFormat;
+    if (userAxisFormat) {
+      axisFormat = userAxisFormat;
+    } else if (dateFormat === 'D') {
+      axisFormat = '%d';
+    } else {
+      axisFormat = conf.axisFormat ?? '%Y-%m-%d';
+    }
+
     let bottomXAxis = axisBottom(timeScale)
       .tickSize(-h + theTopPad + conf.gridLineStartPadding)
-      .tickFormat(timeFormat(diagObj.db.getAxisFormat() || conf.axisFormat || '%Y-%m-%d'));
+      .tickFormat(timeFormat(axisFormat));
 
     const reTickInterval = /^([1-9]\d*)(millisecond|second|minute|hour|day|week|month)$/;
     const resultTickInterval = reTickInterval.exec(
@@ -669,7 +680,7 @@ export const draw = function (text, id, version, diagObj) {
     if (diagObj.db.topAxisEnabled() || conf.topAxis) {
       let topXAxis = axisTop(timeScale)
         .tickSize(-h + theTopPad + conf.gridLineStartPadding)
-        .tickFormat(timeFormat(diagObj.db.getAxisFormat() || conf.axisFormat || '%Y-%m-%d'));
+        .tickFormat(timeFormat(axisFormat));
 
       if (resultTickInterval !== null) {
         const every = resultTickInterval[1];