Dim cultureInfo As DateTimeFormatInfo = New CultureInfo("ja-JP").DateTimeFormat cultureInfo.Calendar() = New JapaneseCalendar() Dim tmp = DateTimePicker1.Value.ToString("ggyy/MM/dd", cultureInfo) Dim dic As New Dictionary(Of String, String) From {{"明治", "M"}, {"大正", "T"}, {"昭和", "S"}, {"平成", "H"}} TextBox1.Text = dic(tmp.Substring(0, 2)) & tmp.Substring(2)