diff --git a/src/notebooks/deepnote/converters/inputConverters.ts b/src/notebooks/deepnote/converters/inputConverters.ts
index f2386a2fb..d1bb3fdab 100644
--- a/src/notebooks/deepnote/converters/inputConverters.ts
+++ b/src/notebooks/deepnote/converters/inputConverters.ts
@@ -18,6 +18,36 @@ import {
 import { DEEPNOTE_VSCODE_RAW_CONTENT_KEY } from './constants';
 import { formatInputBlockCellContent } from '../inputBlockContentFormatter';
 
+/** Converts date strings to YYYY-MM-DD format, preserving values already in that format. */
+function normalizeDateString(dateValue: unknown): string {
+    if (!dateValue || typeof dateValue !== 'string') {
+        return '';
+    }
+
+    if (/^\d{4}-\d{2}-\d{2}$/.test(dateValue)) {
+        return dateValue;
+    }
+
+    // Detect ISO-style strings that start with YYYY-MM-DD (e.g., "2025-09-30T00:00:00+02:00")
+    // and extract just the date portion to avoid timezone shifts
+    if (/^\d{4}-\d{2}-\d{2}/.test(dateValue)) {
+        return dateValue.substring(0, 10);
+    }
+
+    try {
+        const date = new Date(dateValue);
+        if (isNaN(date.getTime())) {
+            return dateValue;
+        }
+        const year = date.getUTCFullYear();
+        const month = String(date.getUTCMonth() + 1).padStart(2, '0');
+        const day = String(date.getUTCDate()).padStart(2, '0');
+        return `${year}-${month}-${day}`;
+    } catch {
+        return dateValue;
+    }
+}
+
 export abstract class BaseInputBlockConverter<T extends z.ZodObject> implements BlockConverter {
     abstract schema(): T;
     abstract getSupportedType(): string;
@@ -248,8 +278,20 @@ export class InputDateBlockConverter extends BaseInputBlockConverter<typeof Deep
         return cell;
     }
 
-    // Date blocks are readonly - edits are reverted by DeepnoteInputBlockEditProtection
-    // Uses base class applyChangesToBlock which preserves existing metadata
+    /**
+     * Normalizes ISO date strings to YYYY-MM-DD format expected by createPythonCode.
+     * Deepnote API may return dates like "2025-09-30T00:00:00.000Z".
+     */
+    override applyChangesToBlock(block: DeepnoteBlock, _cell: NotebookCellData): void {
+        const value = block.metadata?.deepnote_variable_value;
+
+        if (typeof value === 'string' && value) {
+            const normalizedValue = normalizeDateString(value);
+            this.updateBlockMetadata(block, { deepnote_variable_value: normalizedValue });
+        } else {
+            this.updateBlockMetadata(block, {});
+        }
+    }
 }
 
 export class InputDateRangeBlockConverter extends BaseInputBlockConverter<typeof DeepnoteDateRangeInputMetadataSchema> {
@@ -271,8 +313,21 @@ export class InputDateRangeBlockConverter extends BaseInputBlockConverter<typeof
         return cell;
     }
 
-    // Date range blocks are readonly - edits are reverted by DeepnoteInputBlockEditProtection
-    // Uses base class applyChangesToBlock which preserves existing metadata
+    /**
+     * Normalizes ISO date strings to YYYY-MM-DD format expected by createPythonCode.
+     * Deepnote API may return dates like ["2025-09-30T00:00:00.000Z", "2025-10-16T00:00:00.000Z"].
+     * Relative date strings like "past3months" are preserved as-is.
+     */
+    override applyChangesToBlock(block: DeepnoteBlock, _cell: NotebookCellData): void {
+        const value = block.metadata?.deepnote_variable_value;
+
+        if (Array.isArray(value) && value.length === 2) {
+            const normalizedValue: [string, string] = [normalizeDateString(value[0]), normalizeDateString(value[1])];
+            this.updateBlockMetadata(block, { deepnote_variable_value: normalizedValue });
+        } else {
+            this.updateBlockMetadata(block, {});
+        }
+    }
 }
 
 export class InputFileBlockConverter extends BaseInputBlockConverter<typeof DeepnoteFileInputMetadataSchema> {
diff --git a/src/notebooks/deepnote/converters/inputConverters.unit.test.ts b/src/notebooks/deepnote/converters/inputConverters.unit.test.ts
index 483f43b23..3a4848d09 100644
--- a/src/notebooks/deepnote/converters/inputConverters.unit.test.ts
+++ b/src/notebooks/deepnote/converters/inputConverters.unit.test.ts
@@ -700,7 +700,7 @@ suite('InputDateBlockConverter', () => {
     });
 
     suite('applyChangesToBlock', () => {
-        test('preserves existing metadata (date blocks are readonly)', () => {
+        test('normalizes ISO date string to YYYY-MM-DD', () => {
             const block: DeepnoteBlock = {
                 blockGroup: 'test-group',
                 content: '',
@@ -713,17 +713,76 @@ suite('InputDateBlockConverter', () => {
                 sortingKey: 'a0',
                 type: 'input-date'
             };
-            // Cell content is ignored since date blocks are readonly
-            const cell = new NotebookCellData(NotebookCellKind.Code, '"2025-12-31T00:00:00.000Z"', 'python');
+            const cell = new NotebookCellData(NotebookCellKind.Code, '"2025-01-01"', 'python');
 
             converter.applyChangesToBlock(block, cell);
 
             assert.strictEqual(block.content, '');
-            // Value should be preserved from metadata, not parsed from cell
-            assert.strictEqual(block.metadata?.deepnote_variable_value, '2025-01-01T00:00:00.000Z');
+            // ISO date should be normalized to YYYY-MM-DD
+            assert.strictEqual(block.metadata?.deepnote_variable_value, '2025-01-01');
             assert.strictEqual(block.metadata?.deepnote_variable_name, 'date1');
             assert.strictEqual(block.metadata?.deepnote_input_date_version, 2);
         });
+
+        test('preserves dates already in YYYY-MM-DD format', () => {
+            const block: DeepnoteBlock = {
+                blockGroup: 'test-group',
+                content: '',
+                id: 'block-123',
+                metadata: {
+                    deepnote_variable_name: 'date1',
+                    deepnote_input_date_version: 2,
+                    deepnote_variable_value: '2025-06-15'
+                },
+                sortingKey: 'a0',
+                type: 'input-date'
+            };
+            const cell = new NotebookCellData(NotebookCellKind.Code, '"2025-06-15"', 'python');
+
+            converter.applyChangesToBlock(block, cell);
+
+            // YYYY-MM-DD format should remain unchanged
+            assert.strictEqual(block.metadata?.deepnote_variable_value, '2025-06-15');
+        });
+
+        test('handles timezone-aware ISO dates correctly', () => {
+            const block: DeepnoteBlock = {
+                blockGroup: 'test-group',
+                content: '',
+                id: 'block-123',
+                metadata: {
+                    deepnote_variable_name: 'date1',
+                    deepnote_variable_value: '2025-09-30T00:00:00.000Z'
+                },
+                sortingKey: 'a0',
+                type: 'input-date'
+            };
+            const cell = new NotebookCellData(NotebookCellKind.Code, '"2025-09-30"', 'python');
+
+            converter.applyChangesToBlock(block, cell);
+
+            // Should extract the date portion from ISO string
+            assert.strictEqual(block.metadata?.deepnote_variable_value, '2025-09-30');
+        });
+
+        test('preserves empty or null values', () => {
+            const block: DeepnoteBlock = {
+                blockGroup: 'test-group',
+                content: '',
+                id: 'block-123',
+                metadata: {
+                    deepnote_variable_name: 'date1',
+                    deepnote_variable_value: ''
+                },
+                sortingKey: 'a0',
+                type: 'input-date'
+            };
+            const cell = new NotebookCellData(NotebookCellKind.Code, '""', 'python');
+
+            converter.applyChangesToBlock(block, cell);
+
+            assert.strictEqual(block.metadata?.deepnote_variable_value, '');
+        });
     });
 });
 
@@ -791,7 +850,29 @@ suite('InputDateRangeBlockConverter', () => {
     });
 
     suite('applyChangesToBlock', () => {
-        test('preserves existing metadata (date range blocks are readonly)', () => {
+        test('normalizes ISO date range to YYYY-MM-DD format', () => {
+            const block: DeepnoteBlock = {
+                blockGroup: 'test-group',
+                content: '',
+                id: 'block-123',
+                metadata: {
+                    deepnote_variable_name: 'range1',
+                    deepnote_variable_value: ['2025-09-30T00:00:00.000Z', '2025-10-16T00:00:00.000Z']
+                },
+                sortingKey: 'a0',
+                type: 'input-date-range'
+            };
+            const cell = new NotebookCellData(NotebookCellKind.Code, '("2025-09-30", "2025-10-16")', 'python');
+
+            converter.applyChangesToBlock(block, cell);
+
+            assert.strictEqual(block.content, '');
+            // ISO dates should be normalized to YYYY-MM-DD
+            assert.deepStrictEqual(block.metadata?.deepnote_variable_value, ['2025-09-30', '2025-10-16']);
+            assert.strictEqual(block.metadata?.deepnote_variable_name, 'range1');
+        });
+
+        test('preserves date ranges already in YYYY-MM-DD format', () => {
             const block: DeepnoteBlock = {
                 blockGroup: 'test-group',
                 content: '',
@@ -803,16 +884,74 @@ suite('InputDateRangeBlockConverter', () => {
                 sortingKey: 'a0',
                 type: 'input-date-range'
             };
-            // Cell content is ignored since date range blocks are readonly
-            const cell = new NotebookCellData(NotebookCellKind.Code, '("2025-01-01", "2025-12-31")', 'python');
+            const cell = new NotebookCellData(NotebookCellKind.Code, '("2025-06-01", "2025-06-30")', 'python');
 
             converter.applyChangesToBlock(block, cell);
 
             assert.strictEqual(block.content, '');
-            // Value should be preserved from metadata, not parsed from cell
+            // YYYY-MM-DD format should remain unchanged
             assert.deepStrictEqual(block.metadata?.deepnote_variable_value, ['2025-06-01', '2025-06-30']);
             assert.strictEqual(block.metadata?.deepnote_variable_name, 'range1');
         });
+
+        test('normalizes mixed ISO and YYYY-MM-DD dates', () => {
+            const block: DeepnoteBlock = {
+                blockGroup: 'test-group',
+                content: '',
+                id: 'block-123',
+                metadata: {
+                    deepnote_variable_name: 'range1',
+                    deepnote_variable_value: ['2025-01-01T00:00:00.000Z', '2025-12-31']
+                },
+                sortingKey: 'a0',
+                type: 'input-date-range'
+            };
+            const cell = new NotebookCellData(NotebookCellKind.Code, '("2025-01-01", "2025-12-31")', 'python');
+
+            converter.applyChangesToBlock(block, cell);
+
+            // Both should be normalized to YYYY-MM-DD
+            assert.deepStrictEqual(block.metadata?.deepnote_variable_value, ['2025-01-01', '2025-12-31']);
+        });
+
+        test('preserves relative date strings', () => {
+            const block: DeepnoteBlock = {
+                blockGroup: 'test-group',
+                content: '',
+                id: 'block-123',
+                metadata: {
+                    deepnote_variable_name: 'range1',
+                    deepnote_variable_value: 'past3months'
+                },
+                sortingKey: 'a0',
+                type: 'input-date-range'
+            };
+            const cell = new NotebookCellData(NotebookCellKind.Code, '', 'python');
+
+            converter.applyChangesToBlock(block, cell);
+
+            // Relative date strings should be preserved
+            assert.strictEqual(block.metadata?.deepnote_variable_value, 'past3months');
+        });
+
+        test('handles empty date range values', () => {
+            const block: DeepnoteBlock = {
+                blockGroup: 'test-group',
+                content: '',
+                id: 'block-123',
+                metadata: {
+                    deepnote_variable_name: 'range1',
+                    deepnote_variable_value: ['', '']
+                },
+                sortingKey: 'a0',
+                type: 'input-date-range'
+            };
+            const cell = new NotebookCellData(NotebookCellKind.Code, '', 'python');
+
+            converter.applyChangesToBlock(block, cell);
+
+            assert.deepStrictEqual(block.metadata?.deepnote_variable_value, ['', '']);
+        });
     });
 });