(Node.js) Set a Custom Last-Modified Date in a Gzip File

See more Gzip Examples

This example demonstrates how to use the SetDt method to specify a custom last-modified date and time that will be embedded in a Gzip file.

A CkDateTime object is first initialized with a specific date/time using an RFC 822 formatted string. This date/time is then applied to the Gzip object using SetDt.

When a compression method is called (such as CompressStringToFile), the specified date/time is included in the Gzip metadata. This allows the resulting .gz file to carry a meaningful timestamp rather than using the current system time.

Install Chilkat for Node.js and Electron using npm at Chilkat npm packages for Node.js Chilkat npm packages for Electron on Windows, Linux, MacOS

var os = require('os');
if (os.platform() == 'win32') {  
  var chilkat = require('@chilkat/ck-node23-win64'); 
} else if (os.platform() == 'linux') {
    if (os.arch() == 'arm') {
        var chilkat = require('@chilkat/ck-node23-linux-arm');
    } else if (os.arch() == 'arm64') {
        var chilkat = require('@chilkat/ck-node23-linux-arm64');
    } else {
        var chilkat = require('@chilkat/ck-node23-linux-x64');
    }
} else if (os.platform() == 'darwin') {
  var chilkat = require('@chilkat/ck-node23-mac-universal');
}

function chilkatExample() {

    var success = false;

    // This example demonstrates how to set a custom last-modified date/time
    // that will be embedded in a Gzip file.

    var gzip = new chilkat.Gzip();
    var dt = new chilkat.CkDateTime();

    // Set the date/time using a timestamp format (ISO 8601 style):
    dt.SetFromTimestamp("2025-11-15T12:45:26-05:00");

    // Apply the date/time to the Gzip object:
    success = gzip.SetDt(dt);
    if (success == false) {
        console.log(gzip.LastErrorText);
        return;
    }

    // Compress a string so the custom date/time is embedded in the .gz:
    var inputStr = "Example text for Gzip compression.";
    success = gzip.CompressStringToFile(inputStr,"utf-8","output.gz");
    if (success == false) {
        console.log(gzip.LastErrorText);
        return;
    }

    console.log("Gzip file created with custom last-modified date.");

}

chilkatExample();