How to Convert DateTime to Unix Timestamp in C#

To convert a DateTime to a timestamp (i.e., Unix timestamp), the process depends on whether you want the result in seconds or milliseconds.

How to convert DateTime to Unix Timestamp in C#?

If you want to convert a DateTime object to a Unix timestamp (seconds since January 1, 1970), you can do the following:

// c# get utc timestamp
DateTime dateTime = DateTime.UtcNow;

// Convert DateTime to UNIX timestamp (seconds)
long unixTimestamp = (long)(dateTime - new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc)).TotalSeconds; // c# datetime to unix timestamp (seconds)

Output: convert datetime to timestamp c#

• Current UTC time: 1/10/2025 6:56:16 AM
• UNIX timestamp: 1736492176

This calculates the number of seconds elapsed since the Unix epoch (1970-01-01T00:00:00Z) until the specified DateTime object.

You can also use DateTimeOffset to get unix timestamp.

// Convert DateTime to DateTimeOffset for easier UNIX timestamp conversion
DateTimeOffset dto = new DateTimeOffset(DateTime.UtcNow);

// Get UNIX timestamp in seconds
string unixTimeInSeconds = dto.ToUnixTimeSeconds().ToString(); // c# datetime to unix epoch (seconds)

// Get UNIX timestamp in milliseconds
string unixTimeInMilliseconds = dto.ToUnixTimeMilliseconds().ToString(); // c# datetime to unix epoch (milliseconds)

Output: example c# datetime to timestamp

• Current UTC time: 1/10/2025 6:58:23 AM +00:00
• UNIX timestamp: 1736492303
• UNIX timestamp, including milliseconds: 1736492303500

You can create an extension method in C# to convert a DateTime to a timestamp.

Convert DateTime to Unix Timestamp C#

// c# .net datetime to timestamp
public static class DateTimeExtensions
{
    // Converts a DateTime to UNIX time (seconds)
    public static string ToUnixTimeInSeconds(this DateTime dateTime)
    {
        DateTimeOffset dto = new DateTimeOffset(dateTime.ToUniversalTime());
        return dto.ToUnixTimeSeconds().ToString();
    }

    // Converts a DateTime to UNIX time (milliseconds)
    public static string ToUnixTimeInMilliseconds(this DateTime dateTime)
    {
        DateTimeOffset dto = new DateTimeOffset(dateTime.ToUniversalTime());
        return dto.ToUnixTimeMilliseconds().ToString();
    }
}

To use the DateTimeExtensions methods, you simply need to call the extension methods on a DateTime object.

using System;

class Program
{
    static void Main()
    {
        // Example DateTime (current date and time)
        DateTime currentDateTime = DateTime.Now;

        // Convert current DateTime to UNIX time (seconds)
        string unixTimeSeconds = currentDateTime.ToUnixTimeInSeconds();
        Console.WriteLine("UNIX Time (Seconds): " + unixTimeSeconds);

        // Convert current DateTime to UNIX time (milliseconds)
        string unixTimeMilliseconds = currentDateTime.ToUnixTimeInMilliseconds();
        Console.WriteLine("UNIX Time (Milliseconds): " + unixTimeMilliseconds);
    }
}

Output:

UNIX Time (Seconds): 1684416570
UNIX Time (Milliseconds): 1684416570456

In this example:

• currentDateTime.ToUnixTimeInSeconds() converts the DateTime to UNIX time in seconds.
• currentDateTime.ToUnixTimeInMilliseconds() converts the DateTime to UNIX time in milliseconds.

Ensure that your DateTimeExtensions class is in the same project or namespace as your main code, or add a using statement to the correct namespace where it's defined.