diff --git a/addons/web/static/src/views/sample_server.js b/addons/web/static/src/views/sample_server.js
index 1d7c5ce7969..4eb5b8fefb3 100644
--- a/addons/web/static/src/views/sample_server.js
+++ b/addons/web/static/src/views/sample_server.js
@@ -18,6 +18,17 @@ function getSampleFromId(id, sampleTexts) {
     return sampleTexts[(id - 1) % sampleTexts.length];
 }
 
+function serializeGroupValue(value, type) {
+    switch (type) {
+        case "date":
+            return serializeDate(value);
+        case "datetime":
+            return serializeDateTime(value);
+        default:
+            return value;
+    }
+}
+
 /**
  * Helper function returning a regular expression specifically matching
  * a given 'term' in a fieldName. For example `fieldNameRegex('abc')`:
@@ -603,7 +614,7 @@ export class SampleServer {
             }
             for (const r of this.data[params.model].records) {
                 const group = getSampleFromId(r.id, groups);
-                r[groupBy] = group.value;
+                r[groupBy] = serializeGroupValue(group.value, groupByField.type);
             }
             this.existingGroupsPopulated = true;
         }
@@ -666,9 +677,12 @@ export class SampleServer {
         // update count and aggregates for each group
         const fullGroupBy = params.groupBy[0];
         const groupBy = fullGroupBy.split(":")[0];
+        const groupByField = this.data[params.model].fields[groupBy];
         const records = this.data[params.model].records;
         for (const g of groups) {
-            const recordsInGroup = records.filter((r) => r[groupBy] === g.value);
+            const recordsInGroup = records.filter((r) => {
+                return r[groupBy] === serializeGroupValue(g.value, groupByField.type);
+            });
             g[`${groupBy}_count`] = recordsInGroup.length;
             g[fullGroupBy] = g.__rawValue;
             for (const field of params.fields) {
diff --git a/addons/web/static/tests/webclient/actions/window_action_tests.js b/addons/web/static/tests/webclient/actions/window_action_tests.js
index 1beef63ea31..d3dbf7f3ad1 100644
--- a/addons/web/static/tests/webclient/actions/window_action_tests.js
+++ b/addons/web/static/tests/webclient/actions/window_action_tests.js
@@ -2567,4 +2567,68 @@ QUnit.module("ActionManager", (hooks) => {
         });
         assert.containsOnce(target, ".o_list_view");
     });
+
+    QUnit.test("sample server: populate groups", async function (assert) {
+        serverData.models.partner.records = [];
+        serverData.views = {
+            "partner,false,kanban": `
+                <kanban sample="1" default_group_by="write_date:month">
+                    <templates>
+                        <t t-name="kanban-box">
+                            <div><field name="display_name"/></div>
+                        </t>
+                    </templates>
+                </kanban>
+            `,
+            "partner,false,pivot": `
+                <pivot sample="1">
+                    <field name="write_date" type="row"/>
+                </pivot>
+            `,
+            "partner,false,search": `<search/>`,
+        };
+        const webClient = await createWebClient({
+            serverData,
+            mockRPC(_, args) {
+                if (args.method === "web_read_group") {
+                    return {
+                        groups: [
+                            {
+                                date_count: 0,
+                                "write_date:month": "December 2022",
+                                __range: {
+                                    "write_date:month": {
+                                        from: "2022-12-01",
+                                        to: "2023-01-01",
+                                    },
+                                },
+                                __domain: [
+                                    ["write_date", ">=", "2022-12-01"],
+                                    ["write_date", "<", "2023-01-01"],
+                                ],
+                            },
+                        ],
+                        length: 1,
+                    };
+                }
+            },
+        });
+        await doAction(webClient, {
+            res_id: 1,
+            type: "ir.actions.act_window",
+            target: "current",
+            res_model: "partner",
+            views: [
+                [false, "kanban"],
+                [false, "pivot"],
+            ],
+        });
+
+        assert.containsOnce(target, ".o_kanban_view .o_view_sample_data");
+        assert.strictEqual(target.querySelector(".o_column_title").innerText, "December 2022");
+
+        await cpHelpers.switchView(target, "pivot");
+
+        assert.containsOnce(target, ".o_pivot_view .o_view_sample_data");
+    });
 });