Google-sheets – How to insert different cell data from a table into a hyperlink

This answer is coming late to the party, but you can achieve what you want by installing this script:

function onEdit(event) {
  var eventRange = event.range;
  if (eventRange.getColumn() == 4) { // 4 == column D
    var columnARange = SpreadsheetApp.getActiveSheet().getRange(eventRange.getRow(), 1, eventRange.getNumRows(), 1);
    var values = columnARange.getValues();
    for (var i = 0; i < values.length; i++) {
       values[i][0] = new Date();
    }
    columnARange.setValues(values);
  }
}

EDIT: It seems you just want to trigger the script when column D is modified, so I have modified the code accordingly.

To install it, go to Tools -> Script editor, paste the code above, and save. From then on, every time you edit a cell in column D, the current timestamp will be inserted in column A.

=VLOOKUP(DAY(TODAY()), A:B, 2, True)

VLOOKUP args:

• arg1: item to match
• arg2: data-range
• arg3: data to be picked from nth column of matching row
• arg4: is_sorted

more here

Hope this helps!