init

src/app/core/services/time-sync.service.ts

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+import { Injectable, signal, computed } from '@angular/core';
+
+@Injectable({ providedIn: 'root' })
+export class TimeSyncService {
+  // serverTime - clientTime offset (milliseconds)
+  private readonly _offset = signal<number>(0);
+  private _lastSyncAt = 0;
+
+  readonly offset = computed(() => this._offset());
+
+  // Returns a server-adjusted now() using the current offset
+  now(): number {
+    return Date.now() + this._offset();
+  }
+
+  // Set offset based on a serverTime observed at approximately receiveAt
+  setFromServerTime(serverTime: number, receiveAt?: number): void {
+    const observedAt = receiveAt ?? Date.now();
+    const offset = serverTime - observedAt;
+    this._offset.set(offset);
+    this._lastSyncAt = Date.now();
+  }
+
+  // Perform an HTTP-based sync using a simple NTP-style roundtrip
+  async syncWithEndpoint(baseApiUrl: string, timeoutMs = 5000): Promise<void> {
+    try {
+      const controller = new AbortController();
+      const t0 = Date.now();
+      const timer = setTimeout(() => controller.abort(), timeoutMs);
+      const resp = await fetch(`${baseApiUrl}/time`, { signal: controller.signal });
+      const t2 = Date.now();
+      clearTimeout(timer);
+      if (!resp.ok) return;
+      const data = await resp.json();
+      // Estimate one-way latency and offset
+      const serverNow = Number(data?.now) || Date.now();
+      const midpoint = (t0 + t2) / 2;
+      const offset = serverNow - midpoint;
+      this._offset.set(offset);
+      this._lastSyncAt = Date.now();
+    } catch {
+      // ignore sync failures; retain last offset
+    }
+  }
+}