Sample Implementations

using System;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.Security.Cryptography;
using System.Net;
using System.Web;
 
// ...
String entrypoint = "http://api.xmltime.com/";
String accesskey = "NYczonwTxv";
String secretkey = "x4whvXnG7cCOBiNBoi1r";

public String servicecall(String service, NameValueCollection iargs) {
    // Hash computation
    var timestamp = DateTime.UtcNow.ToString("o");
    var message = accesskey + service + timestamp;
    var hmac = new HMACSHA1(System.Text.Encoding.ASCII.GetBytes(secretkey));
    var hash = hmac.ComputeHash(System.Text.Encoding.ASCII.GetBytes(message));

    // Copy arguments and add authentication parameters
    var args = new NameValueCollection(iargs);
    args.Set("accesskey", accesskey);
    args.Set("timestamp", timestamp);
    args.Set("signature", Convert.ToBase64String(hash));

    // Generate URI from the arguments
    List<String> items = new List<String>();
    foreach (String key in args.AllKeys)
        items.Add(String.Concat(HttpUtility.UrlEncode(key), "=", HttpUtility.UrlEncode(args[key])));

    UriBuilder uri = new UriBuilder(entrypoint + service);
    uri.Query = String.Join("&", items.ToArray());

    // Retrieve data and return it
    using (WebClient client = new WebClient()) {
        client.Encoding = System.Text.Encoding.UTF8;
        return client.DownloadString(uri.Uri);
    }
}

// Getting data as String:
String timedata = servicecall("timeservice",
        new NameValueCollection {{"placeid", "norway/oslo"}, {"out", "js"}})

Requires third-party dependency axios.

const crypto = require('crypto'); // https://nodejs.org/api/crypto.html
const axios = require("axios"); // 

const entrypoint = 'http://api.xmltime.com/';
const accesskey = 'NYczonwTxv';
const secretkey = 'x4whvXnG7cCOBiNBoi1r';

function servicecall(service, args) {
  const timestamp = new Date().toISOString();
  const message = `${accesskey}${service}${timestamp}`;
  const signature = crypto.createHmac('sha1', secretkey)
                .update(message)
                .digest('base64');
  Object.assign(args, {
    accesskey,
    timestamp,
    signature
  });

  const query = Object.keys(args)
                  .map((key) => `${encodeURIComponent(key)}=${encodeURIComponent(args[key])}`)
                  .join("&")

  const url = `${entrypoint}/${service}?${query}`
  return axios.get(url).then( (res) => res.data);
}

servicecall("timeservice", { "placeid": "norway/oslo", "out": "js", "version": 2} )
  .then((res) => {
    console.log(JSON.stringify(res, null, 2));
  })
  .catch((e => {
    console.error(e);
  }))

use Digest::HMAC_SHA1;
use LWP::Simple;
use URI::Escape;
use POSIX qw(strftime);

sub servicecall($%);

my ($entrypoint, $accesskey, $secretkey) =
    qw(http://api.xmltime.com/ NYczonwTxv x4whvXnG7cCOBiNBoi1r);

my $timedata = servicecall('timeservice', (placeid=>'norway/oslo', out=>'js');


sub servicecall($%) {
    my ($service, %args) = @_;
    my ($timestamp, $hmac, $signature, $query);

    $timestamp = strftime("%FT%T", gmtime());
    $hmac = Digest::HMAC_SHA1->new($secretkey);
    $hmac->add("$accesskey$service$timestamp");
    $signature = $hmac->b64digest;

    $args{accesskey} = $accesskey;
    $args{timestamp} = $timestamp;
    $args{signature} = $signature;

    $query = join(';', map { "$_=".uri_escape($args{$_}) } keys %args);

    return get("$entrypoint/$service?$query");
}

$entrypoint = 'http://api.xmltime.com/';
$accesskey = 'NYczonwTxv';
$secretkey = 'x4whvXnG7cCOBiNBoi1r';

$timedata = servicecall('timeservice', array('placeid'=>'norway/oslo'));

function servicecall($service, $args) {
    global $entrypoint, $accesskey, $secretkey;

    $timestamp = gmdate('c');
    $message = "$accesskey$service$timestamp";
    $signature = base64_encode(hash_hmac('sha1', $message, $secretkey, true));

    $args['accesskey'] = $accesskey;
    $args['timestamp'] = $timestamp;
    $args['signature'] = $signature;

    $url = "$entrypoint/$service?" . http_build_query($args);

    $ch = curl_init($url);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE);
    $result = curl_exec($ch);
    curl_close($ch);
    return $result;
}

import base64, datetime, hashlib, hmac, urllib

entrypoint = "http://api.xmltime.com/"
accesskey = "NYczonwTxv"
secretkey = "x4whvXnG7cCOBiNBoi1r"

def servicecall(service, args):
    global entrypoint, accesskey, secretkey

    timestamp = datetime.datetime.utcnow().isoformat()
    message = accesskey + service + timestamp
    digester = hmac.new(secretkey, message, hashlib.sha1)

    args['accesskey'] = accesskey
    args['timestamp'] = timestamp
    args['signature'] = base64.b64encode(digester.digest())

    url = entrypoint + '/' + service + '?' + urllib.urlencode(args)
    return urllib.urlopen(url).read()

timedata = servicecall("timeservice", dict(placeid=187, out='js'))

require 'base64'
require 'cgi'
require 'hmac-sha1'
require 'net/http'

$entrypoint = 'http://api.xmltime.com/'
$accesskey = 'NYczonwTxv'
$secretkey = 'x4whvXnG7cCOBiNBoi1r'

def servicecall(service, args)
    timestamp = Time.now.getutc.strftime('%FT%T')
    message = $accesskey + service + timestamp
    digest = HMAC::SHA1.digest($secretkey, message)

    args['accesskey'] = $accesskey
    args['timestamp'] = timestamp
    args['signature'] = Base64.encode64(digest).chomp

    query = args.collect do |key, value|
        [key.to_s, CGI::escape(value.to_s)].join('=')
    end.join(';')

    url = $entrypoint + '/' + service + '?' + query
    Net::HTTP.get(URI.parse(url))
end

timedata = servicecall('timeservice', { 'placeid'=>187, 'out'=>'js' })