Learning how to convert server date and time to local date and time

Question

I have this issue that has been bothering me for months. It’s the issue of TimeZone regarding its conversion to local Date and Time. I have really been trying to get this work.

The last login Date and Time is read from the database and passed in Session like this

con.Open();
                                 string check = "SELECT LoginLast, IsActive from Users WHERE Id = @Id";
                                 using (SqlCommand cmd6 = new SqlCommand(check, con))
                                 {
                                     cmd6.Parameters.AddWithValue("@Id", Session["user"]);
                                     Session["LoginLast"] = Convert.ToDateTime(cmd6.ExecuteScalar());
                                 }

Then on page load of next Page

LoginDateTime.Text = Convert.ToDateTime(Session["LoginLast"]).ToLocalTime().ToString("dddd, MMMM d, yyyy h:mm tt") + ".";

But this did not work, so I had to dig deeper and still could not find solution.

So, here is what I am trying to do now but it's not yielding positive result.

In the code below, I got the client timezone using JavaScript, and the client TimeZone is saved in a HiddenField on load. After that, I got the server timezone. Then using ConvertTime method of TimeZoneInfo, convert time to local time.

But how do I just make it convert to Local Date and Time on page load, and display in a Label control?

Getting Client Time Zone(JavaScript)

<script type="text/javascript">
    window.onload = function () {
        var date = new Date();
        var tzstr = date.toTimeString().split("(");
        var timezone = tzstr[1].toString().replace(")", "");
        document.getElementById('hfTimezone').value = timezone;
    };
</script>
<asp:HiddenField ID="hfTimezone" runat="server" />

protected void GetLocal(object sender, EventArgs e)
{
    // 21-Aug-2019 11:59:59 AM
    DateTime time = ConvertDateTimeToLocal(new DateTime(2019, 08, 21, 11, 59, 59));
}
 
protected DateTime ConvertDateTimeToLocal(DateTime dateTime)
{
    TimeZoneInfo serverTimeZone = TimeZoneInfo.FindSystemTimeZoneById(TimeZoneInfo.Local.Id); // Get Server TimeZone
    TimeZoneInfo clientTimeZone = TimeZoneInfo.FindSystemTimeZoneById(hfTimezone.Value); // Get client TimeZone
    DateTime localTime = TimeZoneInfo.ConvertTime(dateTime, serverTimeZone, clientTimeZone); // Convert to local time
    return localTime;
}

The ConvertTime method of TimeZoneInfo, convert time to local time

protected void GetLocal(object sender, EventArgs e)
{
    // 21-Aug-2019 11:59:59 AM
    DateTime time = ConvertDateTimeToLocal(new DateTime(2019, 08, 21, 11, 59, 59));
}
 
protected DateTime ConvertDateTimeToLocal(DateTime dateTime)
{
    TimeZoneInfo serverTimeZone = TimeZoneInfo.FindSystemTimeZoneById(TimeZoneInfo.Local.Id); // Get Server TimeZone
    TimeZoneInfo clientTimeZone = TimeZoneInfo.FindSystemTimeZoneById(hfTimezone.Value); // Get client TimeZone
    DateTime localTime = TimeZoneInfo.ConvertTime(dateTime, serverTimeZone, clientTimeZone); // Convert to local time
    return localTime;
}

Answer 1

Hi @Donald Symmons,

can you please show in a nutshell and in an understandable way how to convert Date and Time to local Date and Time and display it in a label control on the Web page?

Your code can only be implemented by the button, not in Page_Load, because the server-side code executes first, then the client-side code.

You can simply convert time from one time zone to another.

You can find specific information in the documentation.

ConvertTime(DateTime, TimeZoneInfo, TimeZoneInfo)

DateTime:The date and time to convert.

sourceTimeZone TimeZoneInfo:The time zone of dateTime.

destinationTimeZone TimeZoneInfo:The time zone to convert dateTime to.

You can also specify the time zone directly, for example:

TimeZoneInfo serverTimeZone = TimeZoneInfo.FindSystemTimeZoneById("Arabic Standard Time");

Microsoft Time Zone Index Values

protected void Page_Load(object sender, EventArgs e)
        {       
                TimeZoneInfo serverTimeZone = TimeZoneInfo.FindSystemTimeZoneById(TimeZoneInfo.Local.Id); // Get Server TimeZone              
                DateTime time = new DateTime(2019, 08, 21, 11, 59, 59);
                DateTime dateTime = TimeZoneInfo.ConvertTime(time, serverTimeZone, TimeZoneInfo.Local); // Convert to local time            
                Label1.Text = dateTime.ToString();      
        }

Best regards,
Lan Huang

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Answer 2

you should use the timezone offset (minutes):

document.getElementById('timezoneOffset').value = new Date().getTimezoneOffset();

on the server use the offset to convert to local time.

public static string ToBrowserTime(DateTime date, int offset) => date
    .ToUniversalTime()
    .AddMinutes(-offset)
    .ToString();

this will work if the server and client cultures match. otherwise you will need the user's culture to use the correct format for that culture (say UK or France).

Answer 3

Converting server date and time to local date and time involves a few steps. Here's how you can do it:

Step 1: Get the server date and time The first step is to obtain the date and time from the server. You can use server-side programming languages like PHP, Python, or Node.js to retrieve the server date and time.

Step 2: Determine the server timezone The next step is to determine the timezone of the server. This information can usually be found in the server configuration or settings.

Step 3: Determine the local timezone You'll also need to determine the timezone of the user or client requesting the date and time conversion. This information can be obtained using JavaScript's Intl object or by asking the user to specify their timezone.

Step 4: Calculate the time difference Calculate the time difference between the server timezone and the local timezone. You can do this using the getTimezoneOffset() method in JavaScript.

Step 5: Convert the date and time Finally, use the time difference to convert the server date and time to the local date and time. You can do this using JavaScript's Date object and its various methods like getUTCDate(), getUTCHours(), and toLocaleString().

By following these steps, you can easily convert server date and time to local date and time.

Answer 4

To convert server date and time to local date and time, you need to determine the time zone offset between the server's time zone and the local time zone.

One way to achieve this is by using the getTimezoneOffset() method in JavaScript, which returns the time difference, in minutes, between the UTC (Coordinated Universal Time) and the local time zone.

Once you have the time zone offset, you can add or subtract it from the server's date and time to obtain the corresponding local date and time. For example, if the server's date and time is "2023-05-06 10:00:00 UTC" and the local time zone offset is "-300" minutes, then the corresponding local date and time would be "2023-05-06 05:00:00".

It's important to note that time zones can be complex and often involve daylight saving time adjustments, so it's recommended to use a library such as Moment.js or Luxon to handle time zone conversions accurately and efficiently.