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:
="1.0" ="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 &
Canada)</option>
<option value="-7.00" >Mountain Time
(US &
Canada)</option>
<option value="-6.00" >Central Time
(US & Canada),
Mexico City</option>
<option value="-5.00" >Eastern Time
(US & 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"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;
TimeZoneManager
public class TimeZoneManager
{
<summary>
the time zone.
</summary>
///
<param name="offset">The offset.</param>
///
<returns></returns>
private static string GetTimeZone(double offset)
{
//Adjust result based on the server time
zone
string timeZoneKey =
"timeOffset" +
offset.ToString("F");
string result =
(CallContext.GetData(timeZoneKey) ?? "").ToString();
if (result.Length ==
0)
{
string zonesDocPath =
HttpRuntime.AppDomainAppPath +"app_data/TimeZones.xml";
XPathDocument
timeZonesDoc = new
XPathDocument(zonesDocPath);
try
{
string xPath =
"/root/option[@value='" +
offset.ToString("F") +
"']";
XPathNavigator
searchNavigator = timeZonesDoc.CreateNavigator();
XmlNamespaceManager
nsmgr = new XmlNamespaceManager(searchNavigator.NameTable);
XPathNodeIterator
iterator = searchNavigator.Select(xPath, nsmgr);
if
(iterator.MoveNext())
{
result = iterator.Current.Value;
if (!string.IsNullOrEmpty(result))
{
CallContext.SetData(timeZoneKey, result);
}
}
}
catch (Exception ex)
{
return ex.Message;
}
}
return result;
}
///
<summary>
///
Displays the date time.
///
</summary>
///
<param name="dateTime">The date time.</param>
///
<param name="profile">The profile.</param>
///
<returns></returns>
public static string DisplayDateTime(DateTime dateTime, ProfileCommon profile)
{
//Move to universal time (GMT) with Zero
offset
DateTime utcDateTime =
dateTime.ToUniversalTime();
//Add client side offset
DateTime resultDateTime
= utcDateTime.AddHours(profile.hoursDiffStdTime + 1);
return string.Concat(resultDateTime.ToShortDateString(), ", ", resultDateTime.ToShortTimeString(),
", ",
GetTimeZone(profile.hoursDiffStdTime));
}
}
