handle extremely rare js rollover date bugs

Author: GrantBirki

__tests__/functions/is-timestamp-older.test.js

@@ -4,6 +4,7 @@ import {isTimestampOlder} from '../../src/functions/is-timestamp-older'
 beforeEach(() => {
   jest.clearAllMocks()
   jest.spyOn(core, 'debug').mockImplementation(() => {})
+  jest.spyOn(core, 'error').mockImplementation(() => {})
 })
 
 describe('isTimestampOlder', () => {
@@ -87,4 +88,27 @@ describe('isTimestampOlder', () => {
       '2024-10-16T11:00:00Z is not older than 2024-10-16T11:00:00Z'
     )
   })
+
+  test('accepts valid leap year date', () => {
+    // Feb 29, 2024 is valid (leap year)
+    expect(() =>
+      isTimestampOlder('2024-02-29T12:00:00Z', '2024-10-15T11:00:00Z')
+    ).not.toThrow()
+    expect(
+      isTimestampOlder('2024-02-29T12:00:00Z', '2024-10-15T11:00:00Z')
+    ).toBe(true)
+    expect(
+      isTimestampOlder('2024-10-15T11:00:00Z', '2024-02-29T12:00:00Z')
+    ).toBe(false)
+  })
+
+  test('throws an error on js silent date contructor corrections', () => {
+    // Invalid date: 2024-02-30T12:00:00Z actually becomes 2024-03-01T12:00:00Z (gross)
+    expect(() =>
+      isTimestampOlder('2024-02-30T12:00:00Z', '2024-10-15T11:00:00Z')
+    ).toThrow(/Invalid date format/)
+    expect(() =>
+      isTimestampOlder('2024-10-15T11:00:00Z', '2024-02-30T12:00:00Z')
+    ).toThrow(/Invalid date format/)
+  })
 })

dist/index.js

@@ -27,6 +27,38 @@ export function isTimestampOlder(timestampA, timestampB) {
   const timestampADate = new Date(timestampA)
   const timestampBDate = new Date(timestampB)
 
+  // Extra strict: ensure the parsed date matches the input string exactly (prevents JS date rollover)
+  const toStrictISOString = d => {
+    // Returns YYYY-MM-DDTHH:MM:SSZ
+    return (
+      d.getUTCFullYear().toString().padStart(4, '0') +
+      '-' +
+      (d.getUTCMonth() + 1).toString().padStart(2, '0') +
+      '-' +
+      d.getUTCDate().toString().padStart(2, '0') +
+      'T' +
+      d.getUTCHours().toString().padStart(2, '0') +
+      ':' +
+      d.getUTCMinutes().toString().padStart(2, '0') +
+      ':' +
+      d.getUTCSeconds().toString().padStart(2, '0') +
+      'Z'
+    )
+  }
+  if (
+    isNaN(timestampADate) ||
+    isNaN(timestampBDate) ||
+    toStrictISOString(timestampADate) !== timestampA ||
+    toStrictISOString(timestampBDate) !== timestampB
+  ) {
+    core.error(
+      `Invalid date parsing. Received: '${timestampA}' => ${timestampADate}, '${timestampB}' => ${timestampBDate}`
+    )
+    throw new Error(
+      `Invalid date format. Please ensure the dates are valid UTC timestamps. Received: '${timestampA}', '${timestampB}'`
+    )
+  }
+
   const result = timestampADate < timestampBDate
 
   if (result) {