Hi RichardSa,

Please refer below sample.

HTML

<form id="form1" runat="server">
    <asp:TextBox ID="dateTimeTextBox" runat="server"></asp:TextBox>
    <asp:Button ID="insertDateTimeButton" runat="server" Text="Insert DateTime" OnClientClick="insertDateTime()" />
</form>
<script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
<script type="text/javascript">
    function insertDateTime() {
        var dateTimeValue = $('[id*=dateTimeTextBox]').val();
        var data = { dateTimeValue: dateTimeValue };
        $.ajax({
            url: "Default.aspx/InsertDateTimeMethod",
            type: "POST",
            contentType: "application/json; charset=utf-8",
            data: JSON.stringify(data),
            dataType: "json",
            success: function (response) {
                alert(response.d);
            },
            error: function (response) {
                alert(response.responseText);
            }
        });
    }
</script>

Namespaces

C#

using System.Web.Services;
using System.Globalization;
using System.Configuration;
using System.Data.SqlClient;

VB.Net

Imports System.Web.Services
Imports System.Globalization
Imports System.Configuration
Imports System.Data.SqlClient

Code

C#

[WebMethod]
public static string InsertDateTimeMethod(string dateTimeValue)
{
    DateTime dateTime = new DateTime(2023, 03, 18, 14, 30, 0);
    var data = new { dateTimeValue = dateTime.ToString("dd-MM-yyyy HH:mm:ss") };
    string constring = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
    using (SqlConnection con = new SqlConnection(constring))
    {
        string query = "INSERT INTO DateTimeTable (DateTimeValue) VALUES (@DateTimeValue)";
        SqlCommand cmd = new SqlCommand(query, con);
        cmd.Parameters.AddWithValue("@DateTimeValue", DateTime.ParseExact(dateTimeValue, "dd-MM-yyyy HH:mm:ss", CultureInfo.InvariantCulture));
        con.Open();
        cmd.ExecuteNonQuery();
    }
    return "DateTime value inserted successfully";
}

VB.Net

<WebMethod>
Public Shared Function InsertDateTimeMethod(ByVal dateTimeValue As String) As String
    Dim dateTime As DateTime = New DateTime(2023, 3, 18, 14, 30, 0)
    Dim data = New With {Key .dateTimeValue = dateTime.ToString("dd-MM-yyyy HH:mm:ss")}
    Dim constring As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
    Using con As SqlConnection = New SqlConnection(constring)
        Dim query As String = "INSERT INTO DateTimeTable (DateTimeValue) VALUES (@DateTimeValue)"
        Dim cmd As SqlCommand = New SqlCommand(query, con)
        cmd.Parameters.AddWithValue("@DateTimeValue", DateTime.ParseExact(dateTimeValue, "dd-MM-yyyy HH:mm:ss", CultureInfo.InvariantCulture))
        con.Open()
        cmd.ExecuteNonQuery()
    End Using

    Return "DateTime value inserted successfully"
End Function

Screenshot