To reproduce:

1. Download attached "stopwatch.unity.zip" project and open in Unity
2. Open "New Scene" scene
3. Build for iOS or macOS Standalone (IL2CPP)
4. Deploy the Xcode project to the iOS device or run Standalone Build
5. Observe that there two Timers
6. Change your Testing Environment Time or Time Zone

Expected Results: Two Timers does not change and stays the same
Actual Results: System.Diagnostics.Stopwatch changes when Time or Time Zone is changed - Increases or Decreases

Notes:
- This issue does not reproduce on Windows Editor and Standalone, macOS Editor and Android (IL2CPP)
- This issue happens only on iOS and macOS Standalone (IL2CPP)
- https://forum.unity.com/threads/no-monotonic-clock-on-il2cpp.540207/
- https://forum.unity.com/threads/monotone-crossplatform-clock.659752/#post-4416568

Tested with:
- iPhone XS, iOS: 12.0 - Reproduced
- iPhone 8 Plus, iOS: 12.0 - Reproduced
- iPhone 7 Plus, iOS: 12.0 - Reproduced

Reproduced on Unity 2017.4.0f1, 2017.4.26f1, 2018.3.14f1, 2018.4.0f1, 2019.1.2f1, 2019.2.0b1 and 2019.3.0a1