fix(date): resolve timezone issues in DatePrompt

.changeset/early-ads-tap.md

@@ -0,0 +1,6 @@
+---
+"@clack/prompts": patch
+"@clack/core": patch
+---
+
+Fix timezone issues in DatePrompt causing dates to be off by one day in non-UTC timezones

packages/core/src/prompts/date.ts

@@ -31,13 +31,17 @@ function dateToSegmentValues(date: Date | undefined): DateParts {
 		return { year: '____', month: '__', day: '__' };
 	}
 	return {
-		year: String(date.getFullYear()).padStart(4, '0'),
-		month: String(date.getMonth() + 1).padStart(2, '0'),
-		day: String(date.getDate()).padStart(2, '0'),
+		year: String(date.getUTCFullYear()).padStart(4, '0'),
+		month: String(date.getUTCMonth() + 1).padStart(2, '0'),
+		day: String(date.getUTCDate()).padStart(2, '0'),
 	};
 }
 
-function segmentValuesToParsed(parts: DateParts): { year: number; month: number; day: number } {
+function segmentValuesToParsed(parts: DateParts): {
+	year: number;
+	month: number;
+	day: number;
+} {
 	const val = (s: string) => Number.parseInt((s || '0').replace(/_/g, '0'), 10) || 0;
 	return {
 		year: val(parts.year),
@@ -119,18 +123,22 @@ function segmentValuesToParts(
 	if (!year || year < 1000 || year > 9999) return undefined;
 	if (!month || month < 1 || month > 12) return undefined;
 	if (!day || day < 1) return undefined;
-	const date = new Date(year, month - 1, day);
-	if (date.getFullYear() !== year || date.getMonth() !== month - 1 || date.getDate() !== day) {
+	const date = new Date(Date.UTC(year, month - 1, day));
+	if (
+		date.getUTCFullYear() !== year ||
+		date.getUTCMonth() !== month - 1 ||
+		date.getUTCDate() !== day
+	) {
 		return undefined;
 	}
 	return { year, month, day };
 }
 
-/** Build a Date from segment values using local midnight so getFullYear/getMonth/getDate are timezone-stable. */
+/** Build a Date from segment values using UTC midnight so getFullYear/getMonth/getDate are timezone-stable. */
 function segmentValuesToDate(parts: DateParts): Date | undefined {
 	const parsed = segmentValuesToParts(parts);
 	if (!parsed) return undefined;
-	return new Date(parsed.year, parsed.month - 1, parsed.day);
+	return new Date(Date.UTC(parsed.year, parsed.month - 1, parsed.day));
 }
 
 function segmentValuesToISOString(parts: DateParts): string | undefined {
@@ -278,7 +286,10 @@ export default class DatePrompt extends Prompt<Date> {
 			: clamp(bounds.min, num + direction, bounds.max);
 
 		const newSegmentValue = String(newNum).padStart(segment.len, '0');
-		this.#segmentValues = { ...this.#segmentValues, [segment.type]: newSegmentValue };
+		this.#segmentValues = {
+			...this.#segmentValues,
+			[segment.type]: newSegmentValue,
+		};
 		this.#refreshFromSegmentValues();
 	}
 
@@ -331,7 +342,10 @@ export default class DatePrompt extends Prompt<Date> {
 			const newSegmentVal = segmentDisplay.slice(0, pos) + char + segmentDisplay.slice(pos + 1);
 
 			if (!newSegmentVal.includes('_')) {
-				const newParts = { ...this.#segmentValues, [segment.type]: newSegmentVal };
+				const newParts = {
+					...this.#segmentValues,
+					[segment.type]: newSegmentVal,
+				};
 				const validationMsg = getSegmentValidationMessage(newParts, segment);
 				if (validationMsg) {
 					this.inlineError = validationMsg;

packages/core/test/prompts/date.test.ts

@@ -32,7 +32,7 @@ const DD_MM_YYYY = buildFormatConfig(
 
 const d = (iso: string) => {
 	const [y, m, day] = iso.slice(0, 10).split('-').map(Number);
-	return new Date(y, m - 1, day);
+	return new Date(Date.UTC(y, m - 1, day));
 };
 
 describe('DatePrompt', () => {
@@ -70,7 +70,7 @@ describe('DatePrompt', () => {
 		instance.prompt();
 		expect(instance.userInput).to.equal('2025/01/15');
 		expect(instance.value).toBeInstanceOf(Date);
-		expect(instance.value!.toISOString().slice(0, 10)).to.equal('2025-01-15');
+		expect(instance.value?.toISOString().slice(0, 10)).to.equal('2025-01-15');
 	});
 
 	test('left/right navigates between segments', () => {
@@ -82,18 +82,30 @@ describe('DatePrompt', () => {
 			initialValue: d('2025-01-15'),
 		});
 		instance.prompt();
-		expect(instance.segmentCursor).to.deep.equal({ segmentIndex: 0, positionInSegment: 0 });
+		expect(instance.segmentCursor).to.deep.equal({
+			segmentIndex: 0,
+			positionInSegment: 0,
+		});
 		// Move within year (0->1->2->3), then right from end goes to month
 		for (let i = 0; i < 4; i++) {
 			input.emit('keypress', undefined, { name: 'right' });
 		}
-		expect(instance.segmentCursor).to.deep.equal({ segmentIndex: 1, positionInSegment: 0 });
+		expect(instance.segmentCursor).to.deep.equal({
+			segmentIndex: 1,
+			positionInSegment: 0,
+		});
 		for (let i = 0; i < 2; i++) {
 			input.emit('keypress', undefined, { name: 'right' });
 		}
-		expect(instance.segmentCursor).to.deep.equal({ segmentIndex: 2, positionInSegment: 0 });
+		expect(instance.segmentCursor).to.deep.equal({
+			segmentIndex: 2,
+			positionInSegment: 0,
+		});
 		input.emit('keypress', undefined, { name: 'left' });
-		expect(instance.segmentCursor).to.deep.equal({ segmentIndex: 1, positionInSegment: 0 });
+		expect(instance.segmentCursor).to.deep.equal({
+			segmentIndex: 1,
+			positionInSegment: 0,
+		});
 	});
 
 	test('up/down increments and decrements segment', () => {
@@ -181,14 +193,20 @@ describe('DatePrompt', () => {
 			initialValue: d('2025-01-15'),
 		});
 		instance.prompt();
-		expect(instance.segmentCursor).to.deep.equal({ segmentIndex: 0, positionInSegment: 0 });
+		expect(instance.segmentCursor).to.deep.equal({
+			segmentIndex: 0,
+			positionInSegment: 0,
+		});
 		// Type 2,0,2,3 to change 2025 -> 2023 (edit digit by digit)
 		input.emit('keypress', '2', { name: undefined, sequence: '2' });
 		input.emit('keypress', '0', { name: undefined, sequence: '0' });
 		input.emit('keypress', '2', { name: undefined, sequence: '2' });
 		input.emit('keypress', '3', { name: undefined, sequence: '3' });
 		expect(instance.userInput).to.equal('2023/01/15');
-		expect(instance.segmentCursor).to.deep.equal({ segmentIndex: 0, positionInSegment: 3 });
+		expect(instance.segmentCursor).to.deep.equal({
+			segmentIndex: 0,
+			positionInSegment: 3,
+		});
 	});
 
 	test('backspace clears entire segment at any cursor position', () => {
@@ -201,11 +219,17 @@ describe('DatePrompt', () => {
 		});
 		instance.prompt();
 		expect(instance.userInput).to.equal('2025/12/21');
-		expect(instance.segmentCursor).to.deep.equal({ segmentIndex: 0, positionInSegment: 0 });
+		expect(instance.segmentCursor).to.deep.equal({
+			segmentIndex: 0,
+			positionInSegment: 0,
+		});
 		// Backspace at first position clears whole year segment
 		input.emit('keypress', undefined, { name: 'backspace', sequence: '\x7f' });
 		expect(instance.userInput).to.equal('____/12/21');
-		expect(instance.segmentCursor).to.deep.equal({ segmentIndex: 0, positionInSegment: 0 });
+		expect(instance.segmentCursor).to.deep.equal({
+			segmentIndex: 0,
+			positionInSegment: 0,
+		});
 	});
 
 	test('backspace clears segment when cursor at first char (2___)', () => {
@@ -219,14 +243,23 @@ describe('DatePrompt', () => {
 		// Type "2" to get "2___"
 		input.emit('keypress', '2', { name: undefined, sequence: '2' });
 		expect(instance.userInput).to.equal('2___/__/__');
-		expect(instance.segmentCursor).to.deep.equal({ segmentIndex: 0, positionInSegment: 1 });
+		expect(instance.segmentCursor).to.deep.equal({
+			segmentIndex: 0,
+			positionInSegment: 1,
+		});
 		// Move to first char (position 0)
 		input.emit('keypress', undefined, { name: 'left' });
-		expect(instance.segmentCursor).to.deep.equal({ segmentIndex: 0, positionInSegment: 0 });
+		expect(instance.segmentCursor).to.deep.equal({
+			segmentIndex: 0,
+			positionInSegment: 0,
+		});
 		// Backspace should clear whole segment - also test char-based detection
 		input.emit('keypress', '\x7f', { name: undefined, sequence: '\x7f' });
 		expect(instance.userInput).to.equal('____/__/__');
-		expect(instance.segmentCursor).to.deep.equal({ segmentIndex: 0, positionInSegment: 0 });
+		expect(instance.segmentCursor).to.deep.equal({
+			segmentIndex: 0,
+			positionInSegment: 0,
+		});
 	});
 
 	test('digit input updates segment and jumps to next when complete', () => {
@@ -242,7 +275,10 @@ describe('DatePrompt', () => {
 			input.emit('keypress', c, { name: undefined, sequence: c });
 		}
 		expect(instance.userInput).to.equal('2025/__/__');
-		expect(instance.segmentCursor).to.deep.equal({ segmentIndex: 1, positionInSegment: 0 });
+		expect(instance.segmentCursor).to.deep.equal({
+			segmentIndex: 1,
+			positionInSegment: 0,
+		});
 	});
 
 	test('submit returns ISO string for valid date', async () => {

packages/prompts/test/date.test.ts

@@ -5,7 +5,7 @@ import { MockReadable, MockWritable } from './test-utils.js';
 
 const d = (iso: string) => {
 	const [y, m, day] = iso.slice(0, 10).split('-').map(Number);
-	return new Date(y, m - 1, day);
+	return new Date(Date.UTC(y, m - 1, day));
 };
 
 describe.each(['true', 'false'])('date (isCI = %s)', (isCI) => {