There is the function Sys_Milliseconds:

int curtime;
int Sys_Milliseconds (void)
{
    static int      base;
    static qboolean initialized = false;

    if (!initialized)
    {   // let base retain 16 bits of effectively random data
        base = timeGetTime() & 0xffff0000;
        initialized = true;
    }
    curtime = timeGetTime() - base;

    return curtime;
}

Used in time calculation in the Quake 2 main game loop implementation:

//...
oldtime = Sys_Milliseconds();
//...
while (1) {
        //...

        while (PeekMessage(&msg, NULL, 0, 0, PM_NOREMOVE)) {
            if (!GetMessage(&msg, NULL, 0, 0))
                Com_Quit();
            sys_msg_time = msg.time;
            TranslateMessage(&msg);
            DispatchMessage(&msg);
        }

        do {
            newtime = Sys_Milliseconds();               
            time = newtime - oldtime;
        } while (time < 1);
//...
}

I’m wondering about the usage of the Sys_Milliseconds at all. What’s the point in base = timeGetTime() & 0xffff0000 line? Why are they applying the 0xffff0000 mask on the retrieved time? Why not just use the timeGetTime function directly:

//...
oldtime = timeGetTime();
//...
while (1) {
        //...

        while (PeekMessage(&msg, NULL, 0, 0, PM_NOREMOVE)) {
            if (!GetMessage(&msg, NULL, 0, 0))
                Com_Quit();
            sys_msg_time = msg.time;
            TranslateMessage(&msg);
            DispatchMessage(&msg);
        }

        do {
            newtime = timeGetTime();                
            time = newtime - oldtime;
        } while (time < 1);
//...
}