图表的日期不更新

Question

该图包括显示温室中压力的变化，可以是每天，每周或每月。

但是显示日期的字段（例如今天）不会更新，有时会与当前日期相差一个月。

这是背后的代码。

public partial class SelecionarGrafico : Window
    {
        public int StepGrafico = 0;
        public DateTime DataInicial;
        public DateTime DataMinima;
        public DateTime DataMaxima;
        public SelecionarGrafico(DateTime dataMinima, DateTime dataMaxima)
        {
            InitializeComponent();
            DataMinima = dataMinima;
            DataInicial = dataMinima;
            DataMaxima = dataMaxima;
            DtDataInicial.Value = dataMinima;
            DtDataInicial.Minimum = dataMinima;
            DtDataInicial.Maximum = DataMaxima;
        }

        private void BtnAbrirGrafico_OnClick(object sender, RoutedEventArgs e)
        {
            var chk = -1;
            if (BtnDiario.IsChecked == true) chk = 0;
            else if (BtnSemanal.IsChecked == true) chk = 1;
            else if (BtnMensal.IsChecked == true) chk = 2;
            if (chk == -1)
            {
                MessageBox.Show("Você deve selecionar um tipo de gráfico!", "Atenção!", MessageBoxButton.OK, MessageBoxImage.Stop);
                return;
            }

            if (DtDataInicial.Value == DateTime.MinValue)
            {
                MessageBox.Show("Você deve especificar uma data inicial!", "Atenção!", MessageBoxButton.OK, MessageBoxImage.Stop);
                return;
            }
            if (chk == 0)
                StepGrafico = 1440;
            else if (chk == 1)
            {
                StepGrafico = 10080;
            }
            else if (chk == 2)
            {
                StepGrafico = 43200;
            }
            DataInicial = DtDataInicial.Value ?? DateTime.MinValue;
            Close();
        }
    }

和xaml：

<Window.Background>
        <LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
            <GradientStop Color="#FF0087E4"/>
            <GradientStop Color="#FF29A3DC" Offset="1"/>
        </LinearGradientBrush>
    </Window.Background>
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="Auto"/>
        </Grid.RowDefinitions>
        <TextBlock Grid.Row="0" Foreground="White" Margin="0,10" FontWeight="Bold" HorizontalAlignment="Center" Text="Que tipo de gráfico deseja visualizar?" Grid.ColumnSpan="2"/>
        <Grid Grid.Row="1" HorizontalAlignment="Center">
            <Grid.Resources>
                <Style TargetType="{x:Type RadioButton}" BasedOn="{StaticResource {x:Type ToggleButton}}">
                </Style>
            </Grid.Resources>
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="Auto"/>
                <ColumnDefinition Width="Auto"/>
                <ColumnDefinition Width="Auto"/>
            </Grid.ColumnDefinitions>

            <RadioButton x:Name="BtnDiario" IsChecked="True" Grid.Column="0" Padding="5" Foreground="White" FontWeight="Bold" Content="Diário" BorderBrush="White">
                <RadioButton.Background>
                    <LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
                        <GradientStop Color="#FF03649C" Offset="0"/>
                        <GradientStop Color="#FF00A9DA" Offset="1"/>
                    </LinearGradientBrush>
                </RadioButton.Background>
            </RadioButton>
            <RadioButton x:Name="BtnSemanal" Margin="10,0" Grid.Column="1" Padding="5" Foreground="White" FontWeight="Bold" Content="Semanal" BorderBrush="White">
                <RadioButton.Background>
                    <LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
                        <GradientStop Color="#FF03649C" Offset="0"/>
                        <GradientStop Color="#FF00A9DA" Offset="1"/>
                    </LinearGradientBrush>
                </RadioButton.Background>
            </RadioButton>
            <RadioButton x:Name="BtnMensal" Grid.Column="2" Padding="5" Foreground="White" FontWeight="Bold" Content="Mensal" BorderBrush="White">
                <RadioButton.Background>
                    <LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
                        <GradientStop Color="#FF03649C" Offset="0"/>
                        <GradientStop Color="#FF00A9DA" Offset="1"/>
                    </LinearGradientBrush>
                </RadioButton.Background>
            </RadioButton>
        </Grid>
        <TextBlock Grid.Row="2" Margin="0,10" HorizontalAlignment="Center" Foreground="White" FontWeight="Bold" Text="Selecione a data e o horário iniciais"/>
        <xctk:DateTimePicker x:Name="DtDataInicial"  Grid.Row="3" Margin="10,0" HorizontalAlignment="Stretch" AutoCloseCalendar="True"/>
        <Button Click="BtnAbrirGrafico_OnClick" x:Name="BtnAbrirGrafico"  Grid.Row="4" Margin="0,10" Padding="5" HorizontalAlignment="Center" Foreground="White" FontWeight="Bold" BorderBrush="White">
            <Button.Background>
                <LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
                    <GradientStop Color="#FF03649C" Offset="0"/>
                    <GradientStop Color="#FF00B2DA" Offset="1"/>
                </LinearGradientBrush>
            </Button.Background> Abrir Gráfico
        </Button>
    </Grid>

日期字段中的返回值应为“ 05/04/2019，Friday，11:27”（今天和我写这篇文章的时间）

但在06/03/2019左右。