chore: resolve issue #151 — fix hire-date off-by-one in local timezone

src/components/ui/utils.test.ts

@@ -0,0 +1,55 @@
+import { describe, it, expect } from 'vitest';
+import { formatDate, calculateTenure, parseLocalDate } from './utils';
+
+describe('parseLocalDate', () => {
+  it('parses a date-only string to LOCAL midnight (not UTC midnight)', () => {
+    // Regression for #151: new Date('2023-05-15') is UTC midnight, which is the
+    // previous calendar day in any negative-offset timezone. parseLocalDate must
+    // land on the same calendar day the string names, regardless of the runner TZ.
+    const d = parseLocalDate('2023-05-15');
+    expect(d.getFullYear()).toBe(2023);
+    expect(d.getMonth()).toBe(4); // May (0-indexed)
+    expect(d.getDate()).toBe(15);
+  });
+
+  it('passes strings that carry a time component through to the native parser', () => {
+    const d = parseLocalDate('2023-05-15T12:00:00Z');
+    expect(Number.isNaN(d.getTime())).toBe(false);
+  });
+});
+
+describe('formatDate', () => {
+  it('renders a date-only string on its own calendar day regardless of local timezone', () => {
+    // #151: hire_date "2023-05-15" was rendering as "May 14, 2023" in PDT.
+    expect(formatDate('2023-05-15')).toBe('May 15, 2023');
+  });
+
+  it('formats another date-only value on the correct day', () => {
+    expect(formatDate('2024-01-15')).toBe('Jan 15, 2024');
+  });
+
+  it('does not drift across a year boundary', () => {
+    expect(formatDate('2024-01-01')).toBe('Jan 1, 2024');
+  });
+
+  it('returns an em dash for missing input', () => {
+    expect(formatDate(undefined)).toBe('—');
+    expect(formatDate('')).toBe('—');
+  });
+});
+
+describe('calculateTenure', () => {
+  it('returns an em dash for a missing hire date', () => {
+    expect(calculateTenure(undefined)).toBe('—');
+  });
+
+  it('reads a multi-year date-only hire date without drifting the year down a day', () => {
+    // A hire date ~3.5 years before "now" (built from local parts) should read 3y.
+    const now = new Date();
+    const past = new Date(now.getFullYear() - 3, now.getMonth() - 6, now.getDate());
+    const y = past.getFullYear();
+    const m = String(past.getMonth() + 1).padStart(2, '0');
+    const d = String(past.getDate()).padStart(2, '0');
+    expect(calculateTenure(`${y}-${m}-${d}`).startsWith('3y')).toBe(true);
+  });
+});

src/components/ui/utils.ts

@@ -22,14 +22,32 @@ export function getInitials(name: string): string {
     .slice(0, 2);
 }
 
+/**
+ * Parse a date string into a local Date.
+ *
+ * Date-only strings (`YYYY-MM-DD`) are constructed from their parts so they land
+ * on LOCAL midnight. `new Date('2023-05-15')` instead parses as UTC midnight,
+ * which renders as the previous calendar day in any negative-offset timezone
+ * (e.g. "May 14" in PDT) — issue #151. Strings that carry a time component are
+ * passed through to the native parser unchanged.
+ */
+export function parseLocalDate(dateStr: string): Date {
+  const dateOnly = /^(\d{4})-(\d{2})-(\d{2})$/.exec(dateStr);
+  if (dateOnly) {
+    const [, year, month, day] = dateOnly;
+    return new Date(Number(year), Number(month) - 1, Number(day));
+  }
+  return new Date(dateStr);
+}
+
 /**
  * Format a date string for display.
  * @example formatDate("2024-01-15") => "Jan 15, 2024"
  */
 export function formatDate(dateStr?: string): string {
   if (!dateStr) return '—';
   try {
-    const date = new Date(dateStr);
+    const date = parseLocalDate(dateStr);
     return date.toLocaleDateString('en-US', {
       month: 'short',
       day: 'numeric',
@@ -47,7 +65,7 @@ export function formatDate(dateStr?: string): string {
 export function calculateTenure(hireDate?: string): string {
   if (!hireDate) return '—';
   try {
-    const hire = new Date(hireDate);
+    const hire = parseLocalDate(hireDate);
     const now = new Date();
     const years = Math.floor(
       (now.getTime() - hire.getTime()) / (365.25 * 24 * 60 * 60 * 1000)