The most accurate time on earth is provided by atomic clocks. To synchronize the computer / phone clock with the atomic clock, you can use Network Time Protocol servers.
Supported Android
{5.0 and UP}
Supported Android Version:-
Lollipop (5.0–5.0.2) – Marshmallow (6.0 – 6.0.1) – Nougat (7.0 – 7.1.1) – Oreo (8.0-8.1) – Pie (9.0)

Download Atomic Clock & Watch Accuracy Tool with NTP Time 1.6.11 Platinum APK For Android

Atomic_Clock_Platinum_1.6.11_10611.apk