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DateTime Values according to the remote time zone

Introduction

In the web applications we are often displaying date/time values. But how can we display value according to the user’s time zone?

We can do this by using following steps:

  • Get difference in hours between user’s local time and GMT using Java Script
  • Pass this value from client to the server
  • Attach this value to the remote user object on the server (for example attach it to the Profile object)
  • Detect actual time zone based on  difference between user’s local time and GMT.
  • Calculate time according to the time zone and display time and time zone

Code samples

web.config

Configuring storage of difference between local time and GMT is very simple in asp.net 2.0

<profile enabled="true" >
<properties>
<add 
name="hoursDiffStdTime" 
defaultValue="0" type="double"/>
</properties>
</profile>

login.aspx

Here is simple Javascript to get time difference on the browser.

<head runat="server">
<title>Welcome</title>
<script type="text/javascript">
function 
GetLocalTimeOffset()
{
var rightNow = 
new Date();
var date1 = 
new 
Date(rightNow.getFullYear(), 0, 1, 0, 0, 0, 0);

var temp = 
date1.toGMTString();
var date2 = 
new Date(temp.substring(0, 
temp.lastIndexOf(" ")-1));

var hoursDiffStdTime = 
(date1 - date2) / (1000 * 60 * 60);

createCookie("hoursDiffStdTime", hoursDiffStdTime, 0); 
}

function 
createCookie(name,value,days) {
if (days && 
days > 0) {
var date = new Date();
date.setTime(date.getTime()+(days*24*60*60*1000));
var expires = 
"; expires="+date.toGMTString();
}
else var expires = "";
document.cookie = name+"="+value+expires+"; path=/";
}
</script>
</head>
<body onload="GetLocalTimeOffset();">

default.aspx

Here is how we getting time difference on the server from the client, attaching it to the profile and passing it to calculate display values

Profile.hoursDiffStdTime = Double.Parse(Request.Cookies["hoursDiffStdTime"].Value ); 
Label1.Text = TimeZoneManager.DisplayDateTime(DateTime.Now, Profile);

timezonemanager.cs

Xml doc which holds time zones is located in app_data and looks like this:

<?xml 
version="1.0" encoding="utf-8" ?>
<root>
<option value="-12.00" 
>Eniwetok, Kwajalein</option>
<option value="-11.00" 
>Midway Island, Samoa</option>
<option value="-10.00" 
>Hawaii</option>
<option value="-9.00" >Alaska</option>
<option value="-8.00" >Pacific Time 
(US &amp; 
Canada)</option>
<option value="-7.00" >Mountain Time 
(US &amp; 
Canada)</option>
<option value="-6.00" >Central Time 
(US &amp; Canada), 
Mexico City</option>
<option value="-5.00" >Eastern Time 
(US &amp; Canada), 
Bogota, Lima, Quito</option>
<option value="-4.00" >Atlantic Time 
(Canada), Caracas, La Paz</option>
<option value="-3.50" >Newfoundland</option>
<option value="-3.00" >Brazil, 
Buenos Aires, Georgetown</option>
<option value="-2.00" >Mid-Atlantic</option>
<option value="-1.00" >Azores, Cape 
Verde Islands</option>
<option value="0.00" >Western 
Europe Time, London, Lisbon, Casablanca, Monrovia</option>
<option value="1.00" >CET(Central 
Europe Time), Brussels, Copenhagen, Madrid, Paris</option>
<option value="2.00" >EET(Eastern 
Europe Time), Kaliningrad, South Africa</option>
<option value="3.00" >Baghdad, 
Kuwait, Riyadh, Moscow, St. Petersburg, Volgograd, Nairobi</option>
<option value="3.50" >Tehran</option>
<option value="4.00" >Abu Dhabi, 
Muscat, Baku, Tbilisi</option>
<option value="4.50" >Kabul</option>
<option value="5.00" >Ekaterinburg, 
Islamabad, Karachi, Tashkent</option>
<option value="5.50" >Bombay, 
Calcutta, Madras, New Delhi</option>
<option value="6.00" >Almaty, 
Dhaka, Colombo</option>
<option value="7.00" >Bangkok, 
Hanoi, Jakarta</option>
<option value="8.00" >Beijing, 
Perth, Singapore, Hong Kong, Chongqing, Urumqi, Taipei</option>
<option value="9.00" >Tokyo, Seoul, 
Osaka, Sapporo, Yakutsk</option>
<option value="9.50" >Adelaide, 
Darwin</option>
<option value="10.00" >EAST(East 
Australian Standard), Guam, Papua New Guinea, Vladivostok</option>
<option value="11.00" >Magadan, 
Solomon Islands, New Caledonia</option>
<option value="12.00" >Auckland, 
Wellington, Fiji, Kamchatka, Marshall Island</option>
<option value="13.00" >Nuku&quot;alofa</option>
</root>

We are using XPathDocument class here. XPathDocument works fasrer than XmlDocument so we are using it to get time zone name based on the time difference.

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Runtime.Remoting.Messaging;
using System.Xml.XPath;
using System.Xml;
/// <summary>
/// Summary description for 
TimeZoneManager
/// </summary>
public class TimeZoneManager
{
/// 
<summary>
/// Gets 
the time zone.
/// 
</summary>

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