How to Convert String to Date in C++?

In C++, we generally store the date and time data in the form of the object of type std::tm. Sometimes, this data is stored inside a string object and we need to convert it into the tm type for further processing. In this article, we will learn how to convert a string to date in C++.

Example:

Input:
dateString = "2024-03-14";

Output:
Date: Thu Mar 14 00:00:00 2024

Convert a String to Date in C++

To convert a std::string to date in C++, we can use the std::stringstream class along with the std::get_time() function provided in the <iomanip> a library that parses the string stream interpreting its content as a date and time specification to fill the tm structure.

Syntax of get_time()

ss >> get_time(&tm, "%Y-%m-%d");

Here, 

• ss is the string stream to be converted to date.
• "%Y-%m-%d" is the format of the date in the string.
• tm is the tm structure to store the date.

C++ Program to Convert String to Date

The below program demonstrates how we can convert a string to date using std::get_time() function in C++.

// C++ program to illustrate how to convert string to date
#include <ctime>
#include <iomanip>
#include <iostream>
#include <sstream>
using namespace std;
int main()
{
    // Define a string representing a date
    string dateString = "2024-03-14";
    // Initialize a tm structure to hold the parsed date
    tm tm = {};
    // Create a string stream to parse the date string
    istringstream ss(dateString);
    // Parse the date string using std::get_time
    ss >> get_time(&tm, "%Y-%m-%d");
    // Check if parsing was successful
    if (ss.fail()) {
        cout << "Date parsing failed!" << endl;
        return 1;
    }
    // Convert the parsed date to a time_t value
    time_t date = mktime(&tm);
    // Output the parsed date using std::asctime
    cout << "Date: " << asctime(localtime(&date));
    return 0;
}

Date: Thu Mar 14 00:00:00 2024

Time Complexity: O(N), here N is the length of the date string.
Auxiliary Space: O(1)