C++ 从打包的 DATE 转换为 CTime

Question

I have looked but cannot find the API to convert from DATE to CTime and vice versa. Is there such a thing?

Answer 1

There's probably a shorter method, but going by the docs you can store a DATE in a COleDateTime, get that as a SYSTEMTIME and then use that to construct your CTime. Assuming it's representable as a CTime.

SYSTEMTIME st;
DATE d(whatever);
COleDateTime ole(d);
d.GetAsSystemTime(st);
CTime ct(st);

Answer 2

CTime include a number of constructors and converters for various time formats; it seems odd that DATE is not included. However _time64_t is supported, and differs from DATE only in the starting date and scale. You can easily convert from one to another if you have the starting date of January 1, 1970 as a DATE value:

DATE       jan1_1970 = ????;
__time64_t t;
DATE       d;
double     seconds_per_day = 24.*60.*60.;
t = (d - jan1_1970) * seconds_per_day;
d = (t / seconds_per_day) + jan1_1970;