I'm using EXT 4.8.1.
Using: GridFilters plugin and specifically a dateFilter

The load of store causes wrong values for DateFilter and deselects filter checkboxes(before,on,after)
I'm using a slightly modified example of "GridPanel with Local Filtering, Sorting and Paging"

It also shows:
WARNING: According to WAI-ARIA 1.0 Authoring guide (http://www.w3.org/TR/wai-aria-practices/#menubutton), menu button 'button-1067' should display the menu on SPACE and ENTER keys, which will conflict with the button handler.
Setting Ext.enableAriaButtons = false; Ext.enableAriaPanels = false;
in JS did not change anything.


The steps to reproduce the problem are:

1. Set DateFilter to: before: 2015.01.01.
2. Press AllFilters - it shows the correct time
3. Press "reload store" button - "before" checkbox is now deselected
4. 2. Press AllFilters again - it shows 1970-01-01T02:00:00

aspx:
<%@ Page Language="C#" %>

<%@ Import Namespace="System.Collections.Generic" %>

<script runat="server">
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!X.IsAjaxRequest)
        {
            GridPanel1.GetStore().DataSource = FiltersTestData.Data;
        }
    }

    public void MyData_Refresh(object sender, StoreReadDataEventArgs e)
    {
        resMan.AddScript("alert('Refresh');");
        GridPanel1.GetStore().DataSource = FiltersTestData.Data;
        GridPanel1.GetStore().DataBind();
    }
</script>

<!DOCTYPE html>

<html>
<head runat="server">
    <ext:ResourceManager runat="server" ID="resMan" />
    <title>GridPanel with Local Filtering, Sorting and Paging - Ext.NET Examples</title>

    <script>

        var getFilters = function () {
            var out = [],
                filters = this.up('grid').store.getFilters().items,
                length = filters.length,
                i;

            for (i = 0; i < length; i++) {
                out[i] = filters[i].serialize();
            }

            Ext.Msg.alert('Filters', Ext.encode(out));
        };
    </script>
</head>
<body>

    <h1>GridPanel with Local Filtering, Sorting and Paging</h1>

    <ext:Window
        runat="server"
        Width="950"
        Height="300"
        Closable="false"
        Collapsible="true"
        Title="Example"
        Maximizable="true"
        Layout="Fit">
        <Items>
            <ext:GridPanel ID="GridPanel1" runat="server" Border="false">
                <Store>
                    <ext:Store ID="Store1" runat="server" PageSize="100" GroupField="Name" OnRefreshData="MyData_Refresh">
                        <Model>
                            <ext:Model runat="server" IDProperty="Id">
                                <Fields>
                                    <ext:ModelField Name="Id" Type="Int" />
                                    <ext:ModelField Name="Company" Type="String" />
                                    <ext:ModelField Name="Price" Type="Float" />
                                    <ext:ModelField Name="Date" Type="Date" />
                                    <ext:ModelField Name="Size" Type="String" />
                                    <ext:ModelField Name="Visible" Type="Boolean" />
                                </Fields>
                            </ext:Model>
                        </Model>
                        <Sorters>
                            <ext:DataSorter Property="Company" Direction="ASC" />
                        </Sorters>
                    </ext:Store>
                </Store>
                <ColumnModel runat="server">
                    <Columns>
                        <ext:Column runat="server" Text="ID" DataIndex="Id">
                            <Filter>
                                <ext:NumberFilter />
                            </Filter>
                        </ext:Column>
                        <ext:Column ID="CompanyColumn" runat="server" Text="Company" DataIndex="Company" Flex="1">
                            <Filter>
                                <ext:StringFilter />
                            </Filter>
                        </ext:Column>
                        <ext:Column runat="server" Text="Price" DataIndex="Price">
                            <Renderer Format="UsMoney" />
                            <Filter>
                                <ext:NumberFilter />
                            </Filter>
                        </ext:Column>
                        <ext:DateColumn runat="server" Text="Date" DataIndex="Date" Align="Center" Format="yyyy-MM-dd">
                            <Filter>
                                <ext:DateFilter>
                                    <DatePickerOptions runat="server" TodayText="Now" />
                                </ext:DateFilter>
                            </Filter>
                        </ext:DateColumn>
                        <ext:Column runat="server" Text="Size" DataIndex="Size">
                            <Filter>
                                <ext:ListFilter Options="extra small,small,medium,large,extra large" />
                            </Filter>
                        </ext:Column>
                        <ext:Column runat="server" Text="Visible" DataIndex="Visible" Align="Center">
                            <Renderer Handler="return (value) ? 'Yes':'No';" />
                            <Filter>
                                <ext:BooleanFilter />
                            </Filter>
                        </ext:Column>
                    </Columns>
                </ColumnModel>
                <Plugins>
                    <ext:GridFilters runat="server" />
                </Plugins>
                <BottomBar>
                    <ext:PagingToolbar runat="server" HideRefresh="true" EnableOverflow="true" OverflowHandler="Scroller">
                        <Items>
                            <ext:Button
                                runat="server"
                                Text="All Filters"
                                ToolTip="Get Filters of Grid"
                                Handler="getFilters" />
                            <ext:Button runat="server" Text="Clear Filters" Handler="this.up('grid').filters.clearFilters();" />
                            <ext:Button Text="reload store" runat="server">
                                <Listeners>
                                    <Click Handler="alert('Reload'); App.Store1.load();" />
                                </Listeners>
                            </ext:Button>
                        </Items>
                        <Plugins>
                        </Plugins>
                    </ext:PagingToolbar>
                </BottomBar>
            </ext:GridPanel>
        </Items>
    </ext:Window>
</body>
</html>
Example data loaded (cs):
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;


public class FiltersTestData 
{
    public static List<object> Data
    {
        get
        {
            List<object> goods = new List<object>
            {
                new
                {
                    Id = 1,
                    Price = 71.72,
                    Company = "3m Co",
                    Date = new DateTime(2014, 9, 1),
                    Size = "large",
                    Visible = true
                },
                new
                {
                    Id = 2,
                    Price = 29.01,
                    Company = "Aloca Inc",
                    Date = new DateTime(2014, 08, 01),
                    Size = "medium",
                    Visible = false
                },
                new
                {
                    Id = 3,
                    Price = 83.81,
                    Company = "Altria Group Inc",
                    Date = new DateTime(2014, 08, 03),
                    Size = "large",
                    Visible = false
                },
                new
                {
                    Id = 4,
                    Price = 52.55,
                    Company = "American Express Company",
                    Date = new DateTime(2015, 01, 04),
                    Size = "extra large",
                    Visible = true
                },
                new
                {
                    Id = 5,
                    Price = 64.13,
                    Company = "American International Group Inc.",
                    Date = new DateTime(2015, 03, 04),
                    Size = "small",
                    Visible = true
                },
                new
                {
                    Id = 6,
                    Price = 31.61,
                    Company = "AT&T Inc.",
                    Date = new DateTime(2015, 02, 01),
                    Size = "extra large",
                    Visible = false
                },
                new
                {
                    Id = 7,
                    Price = 75.43,
                    Company = "Boeing Co.",
                    Date = new DateTime(2015, 01, 01),
                    Size = "large",
                    Visible = true
                },
                new
                {
                    Id = 8,
                    Price = 67.27,
                    Company = "Caterpillar Inc.",
                    Date = new DateTime(2014, 12, 03),
                    Size = "medium",
                    Visible = true
                },
                new
                {
                    Id = 9,
                    Price = 49.37,
                    Company = "Citigroup, Inc.",
                    Date = new DateTime(2014, 11, 24),
                    Size = "large",
                    Visible = true
                },
                new
                {
                    Id = 10,
                    Price = 40.48,
                    Company = "E.I. du Pont de Nemours and Company",
                    Date = new DateTime(2014, 05, 09),
                    Size = "extra large",
                    Visible = false
                },
                new
                {
                    Id = 11,
                    Price = 68.1,
                    Company = "Exxon Mobile Corp",
                    Date = new DateTime(2014, 12, 12),
                    Size = "large",
                    Visible = true
                },
                new
                {
                    Id = 12,
                    Price = 34.14,
                    Company = "General Electric Company",
                    Date = new DateTime(2015, 06, 16),
                    Size = "extra large",
                    Visible = true
                },
                new
                {
                    Id = 13,
                    Price = 30.27,
                    Company = "General Motors Corporation",
                    Date = new DateTime(2013, 12, 07),
                    Size = "medium",
                    Visible = true
                },
                new
                {
                    Id = 14,
                    Price = 36.53,
                    Company = "Hewlett-Packard Co.",
                    Date = new DateTime(2014, 05, 13),
                    Size = "large",
                    Visible = true
                },
                new
                {
                    Id = 15,
                    Price = 38.77,
                    Company = "Honweywell Intl Inc",
                    Date = new DateTime(2013, 11, 07),
                    Size = "medium",
                    Visible = false
                },
                new
                {
                    Id = 16,
                    Price = 19.88,
                    Company = "Intel Corporation",
                    Date = new DateTime(2014, 01, 09),
                    Size = "small",
                    Visible = true
                },
                new
                {
                    Id = 17,
                    Price = 81.41,
                    Company = "International Business Machines",
                    Date = new DateTime(2012, 01, 21),
                    Size = "extra large",
                    Visible = true
                },
                new
                {
                    Id = 18,
                    Price = 64.72,
                    Company = "Johnson & Johnson",
                    Date = new DateTime(2015, 01, 10),
                    Size = "extra large",
                    Visible = true
                },
                new
                {
                    Id = 19,
                    Price = 45.73,
                    Company = "JP Morgan & Chase & Co",
                    Date = new DateTime(2015, 02, 20),
                    Size = "large",
                    Visible = false
                },
                new
                {
                    Id = 20,
                    Price = 36.76,
                    Company = "McDonald's Corporation",
                    Date = new DateTime(2014, 06, 12),
                    Size = "large",
                    Visible = true
                },
                new
                {
                    Id = 21,
                    Price = 27.96,
                    Company = "Pfizer Inc",
                    Date = new DateTime(2014, 12, 30),
                    Size = "small",
                    Visible = false
                },
                new
                {
                    Id = 22,
                    Price = 45.07,
                    Company = "The Coca-Cola Company",
                    Date = new DateTime(2014, 01, 30),
                    Size = "medium",
                    Visible = false
                },
                new
                {
                    Id = 23,
                    Price = 34.64,
                    Company = "The Home Depot, Inc",
                    Date = new DateTime(2013, 12, 31),
                    Size = "small",
                    Visible = true
                },
                new
                {
                    Id = 24,
                    Price = 61.91,
                    Company = "The Procter & Gamble Company",
                    Date = new DateTime(2014, 04, 08),
                    Size = "extra large",
                    Visible = true
                },
                new
                {
                    Id = 25,
                    Price = 63.26,
                    Company = "United Technologies Corporation",
                    Date = new DateTime(2013, 06, 04),
                    Size = "medium",
                    Visible = true
                },
                new
                {
                    Id = 26,
                    Price = 35.57,
                    Company = "Verizon Communications",
                    Date = new DateTime(2012, 07, 09),
                    Size = "small",
                    Visible = false
                },
                new
                {
                    Id = 27,
                    Price = 45.45,
                    Company = "Wal-Mart Stores, Inc",
                    Date = new DateTime(2013, 09, 09),
                    Size = "large",
                    Visible = true
                }
            };

            return goods;
        }
    }
}