Fix timezone mismatch: store/compare scheduled_at in UTC

JS was sending browser-local time; dispatcher compared against server UTC,
so posts scheduled in UTC+3 appeared 3h in the future to the dispatcher.

- JS helpers: utcToDate, utcToLocalInput, localInputToUTC
- All scheduled_at values sent to server are now converted to UTC
- Stored values are displayed converted back to browser local time
- relTime and fmtDT parse stored UTC timestamps correctly
- dispatch-social.php: gmdate() for $now (UTC) + sent_at

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

bin/dispatch-social.php

@@ -14,7 +14,7 @@ require ROOT . '/lib/bootstrap.php';
 $lock = fopen(sys_get_temp_dir() . '/hackman_social.lock', 'c');
 if (!$lock || !flock($lock, LOCK_EX | LOCK_NB)) exit(0);
 
-$now = date('Y-m-d H:i:s');
+$now = gmdate('Y-m-d H:i:s');
 
 $stmt = $db->prepare("
     SELECT t.id AS target_id, t.post_id, t.project_id, t.platform, t.target_key, t.include_image,

web/assets/js/app.js

@@ -3840,8 +3840,18 @@ window.addEventListener('DOMContentLoaded', () => {
     d.setSeconds(0, 0);
     return localDTStr(d);
   }
+  // ts is stored UTC ("2026-06-04 17:51:00") — parse with Z so JS treats it as UTC
+  function utcToDate(ts) { return new Date(ts.replace(' ', 'T') + 'Z'); }
+  // Convert stored UTC string → "YYYY-MM-DDTHH:MM" in browser local time (for datetime-local input)
+  function utcToLocalInput(ts) { return localDTStr(utcToDate(ts)); }
+  // Convert datetime-local value (local time) → "YYYY-MM-DD HH:MM:00" UTC for the server
+  function localInputToUTC(dtLocal) {
+    const d = new Date(dtLocal); // browser parses datetime-local as local time
+    const p = n => String(n).padStart(2, '0');
+    return `${d.getUTCFullYear()}-${p(d.getUTCMonth()+1)}-${p(d.getUTCDate())} ${p(d.getUTCHours())}:${p(d.getUTCMinutes())}:00`;
+  }
   function relTime(ts) {
-    const diff = (new Date(ts.replace(' ', 'T')) - Date.now()) / 1000;
+    const diff = (utcToDate(ts) - Date.now()) / 1000;
     const abs  = Math.abs(diff);
     const suf  = diff > 0 ? '' : ' ago';
     const pre  = diff > 0 ? 'in ' : '';
@@ -3851,7 +3861,7 @@ window.addEventListener('DOMContentLoaded', () => {
     return pre + Math.round(abs / 86400) + ' d' + suf;
   }
   function fmtDT(ts) {
-    return ts.substring(0, 16).replace('T', ' ');
+    return localDTStr(utcToDate(ts)).replace('T', ' ');
   }
 
   // ── Emoji picker ─────────────────────────────────────────────────────────────
@@ -4013,7 +4023,7 @@ window.addEventListener('DOMContentLoaded', () => {
   // ── Build edit pane HTML ──────────────────────────────────────────────────────
   function buildEditPane(post) {
     const isNew   = !post;
-    const dt      = post ? post.scheduled_at.replace(' ', 'T').substring(0, 16) : defaultScheduleTime();
+    const dt      = post ? utcToLocalInput(post.scheduled_at) : defaultScheduleTime();
     const content = post?.content || '';
     const imgPath = post?.image_path || '';
     const imgUrl  = post?.image_url  || '';
@@ -4076,21 +4086,21 @@ window.addEventListener('DOMContentLoaded', () => {
   async function doAutosave(card) {
     const post        = card._post;
     if (!post) return;
-    const content     = card.querySelector('.sc-content').value.trim();
+    const content      = card.querySelector('.sc-content').value.trim();
-    const scheduledAt = card.querySelector('.sc-dt').value;
+    const scheduledAt  = card.querySelector('.sc-dt').value;
-    const imagePath   = card.querySelector('.sc-img-path').value;
+    const imagePath    = card.querySelector('.sc-img-path').value;
-    const targets     = collectTargetsFrom(card.querySelector('.sc-targets'));
+    const targets      = collectTargetsFrom(card.querySelector('.sc-targets'));
     if (!content || !scheduledAt || !targets.length) return;
 
     setSaveIndicator(card, 'saving');
-    const body = { action: 'update', id: post.id, content, scheduled_at: scheduledAt, image_path: imagePath, targets };
+    const scheduledUTC = localInputToUTC(scheduledAt);
+    const body = { action: 'update', id: post.id, content, scheduled_at: scheduledUTC, image_path: imagePath, targets };
     const r = await fetch('/api/social', { method: 'POST', headers: { 'Content-Type': 'application/json' }, body: JSON.stringify(body) });
     const d = await r.json();
     if (d.error) { setSaveIndicator(card, 'error'); showCardError(card, d.error); }
     else {
       setSaveIndicator(card, 'saved');
-      // keep in-memory post up to date so cancel reverts to latest saved state
+      card._post = { ...post, content, scheduled_at: scheduledUTC, image_path: imagePath };
-      card._post = { ...post, content, scheduled_at: scheduledAt.replace('T', ' '), image_path: imagePath };
     }
   }
 
@@ -4218,7 +4228,7 @@ window.addEventListener('DOMContentLoaded', () => {
     clearTimeout(card._autosaveTimer);
     setSaveIndicator(card, 'saving');
 
-    const body = { action: isNew ? 'create' : 'update', content, scheduled_at: scheduledAt, image_path: imagePath, targets };
+    const body = { action: isNew ? 'create' : 'update', content, scheduled_at: localInputToUTC(scheduledAt), image_path: imagePath, targets };
     if (!isNew) body.id = post.id;
 
     const r = await fetch('/api/social', { method: 'POST', headers: { 'Content-Type': 'application/json' }, body: JSON.stringify(body) });