CODEWITHSUNDEEP
c++
Harry Boy
Harry Boy

Reputation: 4745

Convert UNIX epoch time to SYSTEMTIME

In my C++ windows app I am converting a SYSTEMTIME to a formatted string like so:

    SYSTEMTIME systemTime;
    GetSystemTime(&systemTime);
    char pSystemTime[50];
    sprintf_s(pSystemTime, 50, "%04d%02d%02d%02d%02d%02d%03u\0", systemTime.wYear, systemTime.wMonth,
                                                                              systemTime.wDay, systemTime.wHour,
                                                                              systemTime.wMinute, systemTime.wSecond,
                                                                              systemTime.wMilliseconds);

Now I have a time in milliseconds since UNIX epoch.

long time = 1442524186;  //for example

How do I convert this long epoch time to a SYSTEMTIME so that I can also format it to a string?

Upvotes: 1

Views: 4849

Answers (2)

sreeR
sreeR

Reputation: 91

In MillisToSystemTime the line should be this way:

UINT64 t = multiplier * millis + 116444736000000000

Upvotes: 0

72DFBF5B A0DF5BE9
72DFBF5B A0DF5BE9

Reputation: 5002

static UINT64 FileTimeToMillis(const FILETIME &ft)
{
    ULARGE_INTEGER uli;
    uli.LowPart = ft.dwLowDateTime; // could use memcpy here!
    uli.HighPart = ft.dwHighDateTime;

    return static_cast<UINT64>(uli.QuadPart/10000);
}

static void MillisToSystemTime(UINT64 millis, SYSTEMTIME *st)
{
    UINT64 multiplier = 10000;
    UINT64 t = multiplier * millis;

    ULARGE_INTEGER li;
    li.QuadPart = t;
    // NOTE, DON'T have to do this any longer because we're putting
    // in the 64bit UINT directly
    //li.LowPart = static_cast<DWORD>(t & 0xFFFFFFFF);
    //li.HighPart = static_cast<DWORD>(t >> 32);

    FILETIME ft;
    ft.dwLowDateTime = li.LowPart;
    ft.dwHighDateTime = li.HighPart;

    ::FileTimeToSystemTime(&ft, st);
}

Source: https://stackoverflow.com/a/11123106/2385309

Edit: Also see: https://stackoverflow.com/a/26486180/2385309 You might need to add/subtract 11644473600000 for Epoch time milliseconds

Upvotes: 5

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