MQL5 ReferenceCommon FunctionsGetTickCount64
The GetTickCount64() function returns the number of milliseconds that have elapsed since the system was launched.
A ulong type value.
The counter is limited to the accuracy of the system timer, which usually returns a result with the 10-16 millisecond precision. Unlike GetTickCount, which is of uint type and the contents of which overflow every 49.7 days in the case of continued computer operation, GetTickCount64() can be used for the unlimited computer operation time and is not subject to overflow.
Date and Time, EventSetMillisecondTimer, GetTickCount, GetMicrosecondCount