Share links carry the world time when made away from live

Field 28, worldTime, holds the world time of a link made away from live:
zigzag seconds since 2026-01-01, like field 8, but it may lie ahead of the
link's creation (a forecast moment). Opening such a link pauses the world
clock at that time; a link without it leaves the clock alone, so a page
opens live and Back or Forward does not stop a replay. Times no JS Date
can hold are dropped.

src/layers/weather/index.js

@@ -52,7 +52,8 @@ const utc = (value) =>
     : t('Unavailable');
 
 /** A per-application observation layer, using the existing layer lifecycle and
- * row controls. History is transient: shared links always open latest imagery. */
+ * row controls. Its time is the world clock's, so a link made away from live
+ * opens its imagery at that time; one made live opens the latest. */
 export function createWeatherLayer({
   feed,
   clock,

src/share/viewCodec.js

@@ -31,6 +31,7 @@ import {
 } from '../data/detectionPolicy.js';
 import { clampScopeFeatherPct } from '../scopeMaskPolicy.js';
 import { VIEW_STYLES } from '../view/index.js';
+import { isWorldTime } from '../time/worldClock.js';
 import { RETIRED_STYLES } from '../visualStylePolicy.js';
 import {
   GLOBAL_POST_DEFAULTS,
@@ -373,6 +374,7 @@ export const SHARE_VIEW_FIELDS = freezeAll([
   { number: 25, key: 'scopeFeatherPct', type: 'uint', default: 100 },
   { number: 26, key: 'scopeTerminusPct', type: 'uint', default: null },
   { number: 27, key: 'styleParams', type: 'bytes', default: BY_STYLE },
+  { number: 28, key: 'worldTime', type: 'epoch', default: null },
 ]);
 const FIELD_BY_KEY = new Map(SHARE_VIEW_FIELDS.map((f) => [f.key, f]));
 const fieldNumber = (key) => FIELD_BY_KEY.get(key).number;
@@ -732,6 +734,9 @@ export function normalizeShareViewState(input = {}) {
     : null;
   state.panelState = normalizePanelState(source.panelState);
   state.sharedAtMs = epochMsOr(source.sharedAtMs);
+  state.worldTime = isWorldTime(source.worldTime)
+    ? Math.floor(source.worldTime / 1000) * 1000
+    : null;
   let view = normalizeView(source.view);
   if (state.layerState) view = liftTrackedEntity(state.layerState, view);
   if (view.kind === 'thing') {
@@ -948,8 +953,9 @@ export function encodeShareView(input) {
           writer.sintField(field.number, signedAngle(state[field.key]));
         break;
       case 'sharedAtMs':
-        if (state.sharedAtMs !== null)
-          writer.sintField(field.number, epochSeconds(state.sharedAtMs));
+      case 'worldTime':
+        if (state[field.key] !== null)
+          writer.sintField(field.number, epochSeconds(state[field.key]));
         break;
       case 'flags': {
         let bits = 0;
@@ -1347,6 +1353,12 @@ export function decodeShareView(code, { nowMs = Date.now() } = {}) {
       raw.sharedAtMs =
         createdAtS >= 1 && Number.isSafeInteger(ms) && ms <= nowMs ? ms : null;
     }
+    // The world time the link was made at, when it was away from live. It
+    // may lie ahead of the link's creation (a forecast) or of now.
+    if (get('worldTime')) {
+      const ms = (SHARE_VIEW_EPOCH_S + unz(get('worldTime').varint)) * 1000;
+      raw.worldTime = isWorldTime(ms) ? ms : null;
+    }
 
     if (get('layerState'))
       raw.layerState = decodeLayers(

src/share/viewCodec.test.mjs

@@ -361,6 +361,7 @@ test('every registered field round-trips at once', () => {
       })),
     },
     sharedAtMs: NOW_MS,
+    worldTime: NOW_MS - 6 * 3_600_000,
   };
   // A thing view derives its camera (roll 0), so the camera fields are
   // checked on the same state as a place view.
@@ -501,6 +502,7 @@ test('the field registry is well formed and permanent', () => {
       [25, 'scopeFeatherPct', 100],
       [26, 'scopeTerminusPct', null],
       [27, 'styleParams', BY_STYLE],
+      [28, 'worldTime', null],
     ],
   );
   assert.deepEqual(
@@ -1338,3 +1340,22 @@ test('a layer option filed under a mirror layer is ignored', () => {
     { scope: 'layer-option', code: `${military}.${layerTokenNumber('m')}` },
   ]);
 });
+
+test('the world time is written only away from live, and may lie ahead', () => {
+  const at = (worldTime) =>
+    decodeShareView(encodeShareView({ sharedAtMs: NOW_MS, worldTime }), {
+      nowMs: NOW_MS,
+    }).state.worldTime;
+  assert.equal(at(null), null);
+  assert.equal(at(NOW_MS - 3_600_000), NOW_MS - 3_600_000);
+  // A forecast moment ahead of the link's creation is kept.
+  assert.equal(at(NOW_MS + 86_400_000), NOW_MS + 86_400_000);
+  // Before the 2026 epoch too: the field is zigzag.
+  assert.equal(at(Date.UTC(2024, 0, 1)), Date.UTC(2024, 0, 1));
+  // Past what a Date can hold: dropped, so the link opens live.
+  assert.equal(at(8.8e15), null);
+  assert.ok(
+    encodeShareView({ sharedAtMs: NOW_MS, worldTime: NOW_MS - 1000 }).length >
+      encodeShareView({ sharedAtMs: NOW_MS }).length,
+  );
+});

src/sharelink.js

@@ -5,6 +5,7 @@ import {
   normalizeAllocationStrategy,
 } from './data/detectionPolicy.js';
 import { clampScopeTerminusPct } from './scopeMask.js';
+import { worldClock as pageWorldClock } from './time/worldClock.js';
 import { clampScopeFeatherPct } from './scopeMaskPolicy.js';
 import {
   decodeLayerStateParams,
@@ -68,9 +69,11 @@ export class ShareLinkManager {
       isNavigationCurrent,
       cancelOwnedNavigation,
       initialShareCode = null,
+      worldClock = pageWorldClock,
     } = {},
   ) {
     this.viewer = viewer;
+    this._worldClock = worldClock;
     // A host may hand over the share code to open instead of the address.
     this._initialShareCode =
       typeof initialShareCode === 'string' ? initialShareCode : null;
@@ -163,8 +166,9 @@ export class ShareLinkManager {
 
   /**
    * The restore state for a share code, in the long form's parsed shape plus
-   * `shareView` (what the view follows, with its offset and last-known fix),
-   * or null when the code is refused.
+   * `shareView` (what the view follows, with its offset and last-known fix)
+   * and `worldTime` (null when the link was made live), or null when the
+   * code is refused.
    */
   _parseShareCode(code) {
     const result = decodeShareView(code);
@@ -174,6 +178,7 @@ export class ShareLinkManager {
     }
     const state = toLegacyShareState(result.state);
     state.shareView = result.state.view;
+    state.worldTime = result.state.worldTime;
     return state;
   }
 
@@ -592,6 +597,10 @@ export class ShareLinkManager {
     // that state in the share format.
     const state = fromLegacyShareState(this._parseShareHash(params.toString()));
     state.sharedAtMs = Math.floor(nowMs / 1000) * 1000;
+    // Away from live, the link opens at the same world time.
+    state.worldTime = this._worldClock.isLive()
+      ? null
+      : Math.floor(this._worldClock.now() / 1000) * 1000;
     let subject = null;
     try {
       subject = this._followSubjectProvider?.({ nowMs }) ?? null;

src/sharelink.navigation.test.mjs

@@ -423,3 +423,28 @@ test('the layer coordinator replaces in-flight share layers with the navigated s
   );
   coordinator.destroy();
 });
+
+test('a link made away from live carries its world time to the page that opens it', (t) => {
+  installTab(t, SHARE_A);
+  const worldTime = Date.UTC(2026, 9, 30, 6, 15, 42);
+  const sharer = new ShareLinkManager(fakeViewer(), {
+    worldClock: { isLive: () => false, now: () => worldTime + 400 },
+  });
+  const link = sharer.buildLink({ nowMs: Date.UTC(2026, 10, 1) });
+  sharer.destroy();
+  const code = new URL(link).pathname.split('/').at(-1);
+  const opener = new ShareLinkManager(fakeViewer(), { initialShareCode: code });
+  assert.equal(opener.parseInitialHash().worldTime, worldTime);
+  opener.destroy();
+
+  const live = new ShareLinkManager(fakeViewer(), {
+    worldClock: { isLive: () => true, now: () => worldTime },
+  });
+  const liveCode = new URL(live.buildLink()).pathname.split('/').at(-1);
+  live.destroy();
+  const liveOpener = new ShareLinkManager(fakeViewer(), {
+    initialShareCode: liveCode,
+  });
+  assert.equal(liveOpener.parseInitialHash().worldTime, null);
+  liveOpener.destroy();
+});

src/ui/shareRestoration.js

@@ -4,6 +4,16 @@ import { canPresentDeferredStatusNotice } from '../loadingFeedback.js';
 import { t, msg, formatDate } from '../i18n/index.js';
 import { SHARE_VIEW_ENTITY_KINDS } from '../share/follow.js';
 import { UiLifetime } from './uiLifetime.js';
+import { isWorldTime, worldClock } from '../time/worldClock.js';
+
+// A link made away from live opens at its world time, paused. One without a
+// world time leaves the clock as it is: a page opens live, and Back or Forward
+// through long-form hashes (which never carry one) does not stop a replay.
+function applySharedWorldTime(state) {
+  if (!isWorldTime(state?.worldTime)) return;
+  worldClock.pause();
+  worldClock.seek(state.worldTime);
+}
 
 /** How long a shared vessel may take to appear in the vessel feed. */
 export const SHARED_VESSEL_WAIT_MS = 120_000;
@@ -146,6 +156,7 @@ export class ShareRestoration {
       : Promise.resolve({ status: 'not-requested', share: null, layers: [] });
     if (savedState) {
       this._hasShareState = true;
+      applySharedWorldTime(savedState);
       // Reserve camera authority now; the delayed mesh-friendly flight may
       // run only if no newer user, voice, or tracking navigation has won.
       this._initialShareNavigationGeneration =
@@ -301,6 +312,7 @@ export class ShareRestoration {
       layers: [],
     });
     this._initialShareState = state;
+    applySharedWorldTime(state);
     this._initialShareSelectionSuperseded = false;
     this._hasShareState = true;
     this._navigatedShareRestoreActive = true;