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  1. #include <iostream>
  2. #include <ctime>
  3.  
  4. struct tm* fromOADate(struct tm* p_Tm, double p_OADate)
  5. {
  6.    static const int64_t OA_UnixTimestamp = -2209161600; /* 30-Dec-1899 */
  7.  
  8.    if (!(   25569 <= p_OADate              /* 01-Jan-1970 00:00:00 */
  9.          &&          p_OADate <= 2958465)) /* 31-Dec-9999 00:00:00 */
  10.    {
  11.       throw std::string("OADate must be between 25569 and 2958465!");
  12.    }
  13.  
  14.    time_t OADatePassedDays = p_OADate;
  15.    double OADateDayTime    = p_OADate - OADatePassedDays;
  16.    time_t OADateSeconds    = OA_UnixTimestamp
  17.                            + OADatePassedDays * 24LL * 3600LL
  18.                            + OADateDayTime * 24.0 * 3600.0;
  19.  
  20.    /* date was greater than 19-Jan-2038 and build is 32 bit */
  21.    if (0 > OADateSeconds)
  22.    {
  23.       throw std::string("OADate must be between 25569 and 50424.134803241!");
  24.    }
  25.  
  26.    return gmtime_r(&OADateSeconds, p_Tm);
  27. }
  28.  
  29.  
  30. int main()
  31. {
  32.    struct tm timeVal;
  33.  
  34.    std::cout << asctime(fromOADate(&timeVal, 25569));           /* 01-Jan-1970 00:00:00 */
  35.    std::cout << asctime(fromOADate(&timeVal, 50424.134803241)); /* 19-Jan-2038 03:14:07 */
  36.  
  37.    return 0;
  38. }
Success #stdin #stdout 0s 15240KB
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Thu Jan  1 00:00:00 1970
Tue Jan 19 03:14:07 2038
https://ideone.com/NsXOu9
language:
C++ (gcc 8.3)
created:
6 years ago
visibility:
public

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