How to convert Unix timestamp to Datetime in C++

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    #include <iostream>
    #include <ctime>
    
    int main() {
        // Unix timestamp representing the number of seconds since the Unix epoch
        time_t unixTimestamp = 1652642245;
    
        // Convert Unix timestamp to a tm structure (UTC)
        tm *dateTime = gmtime(&unixTimestamp);
    
        // Print the converted date and time
        std::cout << "Converted Date: "
                    << dateTime->tm_year + 1900 << "-"
                    << dateTime->tm_mon + 1 << "-"
                    << dateTime->tm_mday << " "
                    << dateTime->tm_hour << ":"
                    << dateTime->tm_min << ":"
                    << dateTime->tm_sec << std::endl;
    
        return 0;
    }

Output:

Converted Date: 2022-05-15 19:17:25

Example only. There may be multiple ways to perform this operation.

Code Explanation

In this C++ example, the Unix timestamp '1652642245' is passed to the gmtime() function, which converts the timestamp to a tm structure representing the date and time in UTC.
The tm_year is the number of years since 1900, and the tm_mon is the month (0-based), so both are adjusted accordingly. The result is a human-readable date of '2022-05-15 19:17:25'. The gmtime() function ensures the timestamp is interpreted in UTC; you can use localtime() instead for local time conversions.

Convert Date to Unix timestamp in C++

Other useful C++ date functions

Function	Description	Example
`time()`	Returns the current Unix timestamp (seconds since January 1, 1970).	`time_t now = time(nullptr);` returns 1693227296 (current timestamp)
`localtime()`	Converts a Unix timestamp to a `tm` structure representing local time.	`localtime(&now)` returns a `tm` structure for local time
`gmtime()`	Converts a Unix timestamp to a `tm` structure representing UTC (Coordinated Universal Time).	`gmtime(&now)` returns a `tm` structure for UTC time
`mktime()`	Converts a `tm` structure representing local time into a Unix timestamp.	`time_t timestamp = mktime(&tm_struct);` converts `tm` to a timestamp
`strftime()`	Formats a `tm` structure into a string according to a format string.	`strftime(buffer, sizeof(buffer), "%Y-%m-%d %H:%M:%S", &tm_struct);` returns a formatted string
`difftime()`	Returns the difference in seconds between two Unix timestamps.	`double diff = difftime(time1, time2);` returns the time difference in seconds
`asctime()`	Converts a `tm` structure to a string representing the local date and time.	`asctime(&tm_struct)` returns a string, e.g., Wed Aug 28 12:34:56 2024
`ctime()`	Converts a Unix timestamp to a string representing the local date and time.	`ctime(&now)` returns a string, e.g., Wed Aug 28 12:34:56 2024
`std::chrono::system_clock::now()`	Returns the current time point as a `std::chrono::time_point` object.	`auto now = std::chrono::system_clock::now();` returns the current time
`std::chrono::duration_cast()`	Converts one duration type to another (e.g., seconds to milliseconds).	`std::chrono::duration_cast(duration);` converts duration

Current Unix Timestamp SECONDS SINCE JAN 01 1970

Current UTC Time

2025-08-20