C# 日期获得一天的起始时间
dateTimePicker1.Value = Convert.ToDateTime(DateTime.Now.ToString("yyyy-MM-dd 00:00:00"));
dateTimePicker2.Value = Convert.ToDateTime(DateTime.Now.ToString("yyyy-MM-dd 23:59:59"));
dateTimePicker1.Value = Convert.ToDateTime(DateTime.Now.ToString("yyyy-MM-dd 00:00:00"));
dateTimePicker2.Value = Convert.ToDateTime(DateTime.Now.ToString("yyyy-MM-dd 23:59:59"));