Compare two dates in C++
When comparing two dates that are of the data type string they will need to be first converted to dates. Once this is done a simple comparison test is possible.
Code:
void compareDates(string date1, string date2) { | |
//create a time_t object | |
time_t rawtime; | |
time(&rawtime); | |
| |
//create a tm structure and load in date1 | |
struct tm * timeinfo1; | |
timeinfo1 = localtime(&rawtime); | |
timeinfo1->tm_year = atoi(date1.substr(6).c_str()) - 1900; | |
timeinfo1->tm_mon = atoi(date1.substr(3, 2).c_str()) - 1; | |
timeinfo1->tm_mday = atoi(date1.substr(0, 2).c_str()); | |
| |
//create a tm structure and load in date2 | |
struct tm * timeinfo2; | |
timeinfo2 = localtime(&rawtime); | |
timeinfo2->tm_year = atoi(date2.substr(6).c_str()) - 1900; | |
timeinfo2->tm_mon = atoi(date2.substr(3, 2).c_str()) - 1; | |
timeinfo2->tm_mday = atoi(date2.substr(0, 2).c_str()); | |
| |
//compare the dates | |
if(timeinfo1 > timeinfo2) cout << "date1 is the latest date"; | |
else cout << "date2 is the latest date"; | |
} |
This function takes two strings, date1 and date2. Both dates are in the format of dd-mm-yyyy. Note that the hyphens can be any character as the sub-strings ignores them.
The function works by creating two tm objects and loading in some demo time data from our time_t object at the beginning of the function. This creates two identical time/date objects. We then overwrite the dates in these objects with our two dates. Once complete we have our two identical date/time objects but now with our two dates overwriting the date parts.
The final lines simply compare the two dates and outputs whichever one is the latest.
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