diff --git a/addons/web/static/src/core/datetime/datetime_picker.xml b/addons/web/static/src/core/datetime/datetime_picker.xml
index b57dba131bb..f2ecf93f4b1 100644
--- a/addons/web/static/src/core/datetime/datetime_picker.xml
+++ b/addons/web/static/src/core/datetime/datetime_picker.xml
@@ -137,7 +137,7 @@
     <t t-name="web.DateTimePicker">
         <div
             class="o_datetime_picker d-flex flex-column gap-2 p-2 p-lg-3 user-select-none"
-            t-attf-style="--DateTimePicker__Day-template-columns: {{ !props.showWeekNumbers or props.range ? 7 : 8 }}"
+            t-attf-style="--DateTimePicker__Day-template-columns: {{ props.showWeekNumbers ?? !props.range ? 8 : 7 }}"
         >
             <nav class="o_datetime_picker_header btn-group">
                 <button class="o_previous btn btn-light flex-grow-0" t-on-click="previous">
diff --git a/addons/web/static/tests/core/datetime/datetime_picker_tests.js b/addons/web/static/tests/core/datetime/datetime_picker_tests.js
index 7412e92be83..235fcb80d8d 100644
--- a/addons/web/static/tests/core/datetime/datetime_picker_tests.js
+++ b/addons/web/static/tests/core/datetime/datetime_picker_tests.js
@@ -75,6 +75,7 @@ QUnit.module("Components", ({ beforeEach }) => {
     //-------------------------------------------------------------------------
 
     QUnit.test("default params", async (assert) => {
+        const fixture = getFixture();
         await mountPicker();
 
         assertDateTimePicker({
@@ -102,6 +103,12 @@ QUnit.module("Components", ({ beforeEach }) => {
             getTexts(minuteSelect, "option"),
             range(12, (i) => pad2(i * 5))
         );
+        assert.strictEqual(
+            fixture
+                .querySelector(".o_datetime_picker")
+                .style.getPropertyValue("--DateTimePicker__Day-template-columns"),
+            "8"
+        );
     });
 
     QUnit.test("minDate: correct days/month/year/decades are disabled", async (assert) => {
@@ -635,6 +642,7 @@ QUnit.module("Components", ({ beforeEach }) => {
     });
 
     QUnit.test("additional month, empty range value", async (assert) => {
+        const fixture = getFixture();
         await mountPicker({
             value: [null, null],
             range: true,
@@ -683,9 +691,16 @@ QUnit.module("Components", ({ beforeEach }) => {
             getTexts(secondTimePicker[1], "option"),
             range(12, (i) => pad2(i * 5))
         );
+        assert.strictEqual(
+            fixture
+                .querySelector(".o_datetime_picker")
+                .style.getPropertyValue("--DateTimePicker__Day-template-columns"),
+            "7"
+        );
     });
 
     QUnit.test("range value", async (assert) => {
+        const fixture = getFixture();
         await mountPicker({
             value: [
                 DateTime.fromObject({ day: 5, hour: 17, minute: 18 }),
@@ -737,9 +752,16 @@ QUnit.module("Components", ({ beforeEach }) => {
             getTexts(secondTimePicker[1], "option"),
             range(12, (i) => pad2(i * 5))
         );
+        assert.strictEqual(
+            fixture
+                .querySelector(".o_datetime_picker")
+                .style.getPropertyValue("--DateTimePicker__Day-template-columns"),
+            "7"
+        );
     });
 
     QUnit.test("range value on small device", async (assert) => {
+        const fixture = getFixture();
         isSmall = true;
 
         await mountPicker({
@@ -782,6 +804,12 @@ QUnit.module("Components", ({ beforeEach }) => {
             getTexts(secondTimePicker[1], "option"),
             range(12, (i) => pad2(i * 5))
         );
+        assert.strictEqual(
+            fixture
+                .querySelector(".o_datetime_picker")
+                .style.getPropertyValue("--DateTimePicker__Day-template-columns"),
+            "7"
+        );
     });
 
     QUnit.test("range value, previous month", async (assert) => {
@@ -1272,6 +1300,7 @@ QUnit.module("Components", ({ beforeEach }) => {
     });
 
     QUnit.test("disable show week numbers", async (assert) => {
+        const fixture = getFixture();
         await mountPicker({ showWeekNumbers: false });
 
         assertDateTimePicker({
@@ -1292,5 +1321,11 @@ QUnit.module("Components", ({ beforeEach }) => {
             ],
             time: [[13, 0]],
         });
+        assert.strictEqual(
+            fixture
+                .querySelector(".o_datetime_picker")
+                .style.getPropertyValue("--DateTimePicker__Day-template-columns"),
+            "7"
+        );
     });
 });