How to format DateTime columns in DataGridView?

If it is a windows form Datagrid, you could use the below code to format the datetime for a column

dataGrid.Columns[2].DefaultCellStyle.Format = "MM/dd/yyyy HH:mm:ss";

EDIT :

Apart from this, if you need the datetime in AM/PM format, you could use the below code

dataGrid.Columns[2].DefaultCellStyle.Format = "MM/dd/yyyy hh:mm:ss tt";

Use Column.DefaultCellStyle.Format property or set it in designer