From bf7f44c584d973ba40e67addaec1306ff7bec1c0 Mon Sep 17 00:00:00 2001
From: dualfroz <me@dualfroz.com>
Date: Fri, 4 Sep 2026 09:43:57 +0200
Subject: [PATCH] fix(set): clamp hour() to 23 instead of the invalid 24

hour(n) with n >= 24 clamped n to 24, which walkTo() rejects as an invalid
hour (valid range 0-23), nulling the epoch and invalidating the object.
Clamp to 23 to match the other overflow-clamping setters (date, month).
---
 package-lock.json      | 39 ---------------------------------------
 src/methods/set/set.js |  3 ++-
 test/set.test.js       | 13 +++++++++++++
 3 files changed, 15 insertions(+), 40 deletions(-)

diff --git a/package-lock.json b/package-lock.json
index 6b0077b..e83a1ff 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -688,9 +688,6 @@
         "arm"
       ],
       "dev": true,
-      "libc": [
-        "glibc"
-      ],
       "license": "MIT",
       "optional": true,
       "os": [
@@ -705,9 +702,6 @@
         "arm"
       ],
       "dev": true,
-      "libc": [
-        "musl"
-      ],
       "license": "MIT",
       "optional": true,
       "os": [
@@ -722,9 +716,6 @@
         "arm64"
       ],
       "dev": true,
-      "libc": [
-        "glibc"
-      ],
       "license": "MIT",
       "optional": true,
       "os": [
@@ -739,9 +730,6 @@
         "arm64"
       ],
       "dev": true,
-      "libc": [
-        "musl"
-      ],
       "license": "MIT",
       "optional": true,
       "os": [
@@ -756,9 +744,6 @@
         "loong64"
       ],
       "dev": true,
-      "libc": [
-        "glibc"
-      ],
       "license": "MIT",
       "optional": true,
       "os": [
@@ -773,9 +758,6 @@
         "loong64"
       ],
       "dev": true,
-      "libc": [
-        "musl"
-      ],
       "license": "MIT",
       "optional": true,
       "os": [
@@ -790,9 +772,6 @@
         "ppc64"
       ],
       "dev": true,
-      "libc": [
-        "glibc"
-      ],
       "license": "MIT",
       "optional": true,
       "os": [
@@ -807,9 +786,6 @@
         "ppc64"
       ],
       "dev": true,
-      "libc": [
-        "musl"
-      ],
       "license": "MIT",
       "optional": true,
       "os": [
@@ -824,9 +800,6 @@
         "riscv64"
       ],
       "dev": true,
-      "libc": [
-        "glibc"
-      ],
       "license": "MIT",
       "optional": true,
       "os": [
@@ -841,9 +814,6 @@
         "riscv64"
       ],
       "dev": true,
-      "libc": [
-        "musl"
-      ],
       "license": "MIT",
       "optional": true,
       "os": [
@@ -858,9 +828,6 @@
         "s390x"
       ],
       "dev": true,
-      "libc": [
-        "glibc"
-      ],
       "license": "MIT",
       "optional": true,
       "os": [
@@ -875,9 +842,6 @@
         "x64"
       ],
       "dev": true,
-      "libc": [
-        "glibc"
-      ],
       "license": "MIT",
       "optional": true,
       "os": [
@@ -892,9 +856,6 @@
         "x64"
       ],
       "dev": true,
-      "libc": [
-        "musl"
-      ],
       "license": "MIT",
       "optional": true,
       "os": [
diff --git a/src/methods/set/set.js b/src/methods/set/set.js
index 1c7d087..b6c83c6 100644
--- a/src/methods/set/set.js
+++ b/src/methods/set/set.js
@@ -67,8 +67,9 @@ const minutes = function (s, n, goFwd) {
 
 const hours = function (s, n, goFwd) {
   n = validate(n)
+  // Clamp to 0-23: hour 24 is rejected by walkTo(), which nulls the epoch.
   if (n >= 24) {
-    n = 24
+    n = 23
   } else if (n < 0) {
     n = 0
   }
diff --git a/test/set.test.js b/test/set.test.js
index 9efdcee..d09a3c1 100644
--- a/test/set.test.js
+++ b/test/set.test.js
@@ -238,3 +238,16 @@ test('month()/date() setters clamp the day to the month length', (t) => {
   t.equal(iso(spacetime('2021-02-10').date(31)), '2021-02-28', 'date(31) in a common february clamps to the 28th')
   t.end()
 })
+
+test('hour() setter clamps out-of-range hours to a valid hour', (t) => {
+  const s = spacetime('2021-03-14 10:00:00', 'UTC')
+  // an out-of-range hour must clamp to 23, not null the epoch
+  t.equal(s.hour(24).hour(), 23, 'hour(24) clamps to 23')
+  t.equal(s.hour(25).hour(), 23, 'hour(25) clamps to 23')
+  t.equal(s.hour(100).hour(), 23, 'hour(100) clamps to 23')
+  t.equal(s.hour(24).isValid(), true, 'hour(24) stays valid')
+  t.equal(s.hour(24).format('iso-short'), '2021-03-14', 'hour(24) keeps the same day')
+  // negative hours still clamp to 0
+  t.equal(s.hour(-1).hour(), 0, 'hour(-1) clamps to 0')
+  t.end()
+})