fix(no-unlocalized-strings): ignore date/time format strings

Detect and ignore common date-fns/moment format strings like
"MMMM d, yyyy", "yyyy-MM-dd", "HH:mm:ss". Uses conservative patterns:
- 3+ consecutive format token chars (yyyy, MMMM, EEE)
- Time patterns: HH:mm, hh:mm
- Date patterns: yyyy-MM, MM-dd, MM/dd

Author: swernerx

src/rules/no-unlocalized-strings.test.ts

@@ -238,6 +238,16 @@ ruleTester.run("no-unlocalized-strings", noUnlocalizedStrings, {
     { code: 'const x = "my-css-class"', filename: "test.tsx" },
     { code: 'const x = "CONSTANT_VALUE"', filename: "test.tsx" },
 
+    // Date/time format strings (date-fns, moment, etc.)
+    { code: 'format(date, "MMMM d, yyyy")', filename: "test.tsx" },
+    { code: 'format(date, "yyyy-MM-dd")', filename: "test.tsx" },
+    { code: 'format(date, "HH:mm:ss")', filename: "test.tsx" },
+    { code: 'format(date, "EEE, MMM d")', filename: "test.tsx" },
+    { code: 'format(date, "PPP")', filename: "test.tsx" },
+    { code: "format(date, \"yyyy-MM-dd'T'HH:mm:ss\")", filename: "test.tsx" },
+    { code: "const fmt = 'MMMM d, yyyy'", filename: "test.tsx" },
+    // Note: Single-letter formats like "h:mm a" are not detected to avoid false positives
+
     // URLs and paths
     { code: 'const url = "https://example.com"', filename: "test.tsx" },
     { code: 'const path = "/api/users"', filename: "test.tsx" },

src/rules/no-unlocalized-strings.ts

@@ -244,6 +244,41 @@ function isInsideLinguiContext(
 // Heuristic: Does this string look like user-visible text?
 // ============================================================================
 
+/**
+ * Checks if a string looks like a date/time format string.
+ *
+ * Uses very conservative patterns to avoid false positives:
+ * - 3+ consecutive same format token char (yyyy, MMMM, EEE) - very distinctive
+ * - Common time patterns: HH:mm, hh:mm, mm:ss
+ * - Common date patterns: MM/dd, yyyy-MM, etc.
+ *
+ * This prevents false positives on format strings from date-fns, moment, etc.
+ */
+function looksLikeDateFormatString(value: string): boolean {
+  // Date format strings are typically short
+  if (value.length > 25) {
+    return false
+  }
+
+  // Very distinctive: 3+ consecutive same letter (yyyy, MMMM, EEE, etc.)
+  // These are extremely rare in natural language
+  if (/([yYMdDHhmsSwWEeQqLcIiRtTpPaAgGkKxXzZO])\1\1+/.test(value)) {
+    return true
+  }
+
+  // Time format: HH:mm, hh:mm, HH:mm:ss
+  if (/[Hh]{2}:[mM]{2}/.test(value)) {
+    return true
+  }
+
+  // Date format with separators: yyyy-MM, MM-dd, MM/dd, etc.
+  if (/[yY]{2,4}[-/][mM]{2}/.test(value) || /[mM]{2}[-/][dD]{2}/.test(value)) {
+    return true
+  }
+
+  return false
+}
+
 /**
  * Determines if a string looks like user-visible UI text.
  *
@@ -300,6 +335,12 @@ function looksLikeUIString(value: string): boolean {
     return false
   }
 
+  // Date/time format strings (e.g., "MMMM d, yyyy", "HH:mm:ss", "yyyy-MM-dd")
+  // Detected by: short string with repeated format tokens and no long natural words
+  if (looksLikeDateFormatString(trimmed)) {
+    return false
+  }
+
   // Non-Latin scripts are almost always user-visible text
   // Ranges: CJK, Hangul, Cyrillic, Arabic, Hebrew, Thai, Hangul Jamo
   if (/[\u3000-\u9fff\uac00-\ud7af\u0400-\u04ff\u0600-\u06ff\u0590-\u05ff\u0e00-\u0e7f\u1100-\u11ff]/.test(trimmed)) {