Question

The question is simple, there are many API specific methods in other languages, but I found none that that were simple and straight forward for Cross-platform C++ usage.

If I have two dates, and they are assumed to be in the same locale, what is the easiest way to differentiate them in C++?

I have (somewhat) looked at using time.h, creating two tm objects, converting them to UTC and then differentiating them.

The current format for the dates is: YY/MM/DD HH:mm:SS (stored as individual integers)

EDIT:

Ok, based on current answers, I’ve done the following (for now):

time_t calculate_seconds_between(
    const uint Y1, const uint M1, const uint D1, const uint H1, const uint m1, const uint S1, // YY/MM/DD HH:mm:SS
    const uint Y2, const uint M2, const uint D2, const uint H2, const uint m2, const uint S2
)
{
    time_t raw;
    time(&raw);

    struct tm t1 = *gmtime(&raw), t2 = t1;

    t1.tm_year = Y1 - 1900;
    t1.tm_mon = M1 - 1;
    t1.tm_mday = D1;
    t1.tm_hour = H1;
    t1.tm_min = m1;
    t1.tm_sec = S1;

    t2.tm_year = Y2 - 1900;
    t2.tm_mon = M2 - 1;
    t2.tm_mday = D2;
    t2.tm_hour = H2;
    t2.tm_min = m2;
    t2.tm_sec = S2;

    time_t tt1, tt2;
    tt1 = mktime(&t1);
    tt2 = mktime(&t2);

    return (tt2 - tt1);
}

Which works great.

Answer 1

To convert from YY/MM/DD HH:mm:SS to struct tm you can use strptime (or make an equivalent if you don’t have it)

const char * dateInput;
// ....
struct tm tm;
time_t val;

memset(&tm, 0, sizeof(struct tm));
strptime(dateInput,"%y/%m/%d %H:%M:%S",&tm);
val = mktime(&tm);

After you have the two time_t values you can call difftime.