Range().Value = Now Returning Time In Multiple Rows

The purpose of my code is to time production cycles for heavy equipment. There are five - six segments in the cycle, and it's possible that not every segment is included in each cycle. It's also possible that the cycle will not go in sequential order.

Here's a snippet of

Sub MacroD()
Dim LR As Long
LR = Range("D" & Rows.Count).End(xlUp).Row + 1
ActiveSheet.Unprotect
Range("D18:D" & LR).Value = Now
UserForm1.ListBox1.Text = "Time"
UserForm1.ListBox1.SetFocus
' UserForm1.Show
End Sub

Sub MacroF()
Dim LR As Long
LR = Range("F" & Rows.Count).End(xlUp).Row + 1
ActiveSheet.Unprotect
Range("F18:F" & LR).Value = Now
UserForm1.ListBox1.Text = "Time"
UserForm1.ListBox1.SetFocus
' UserForm1.Show
End Sub

My problem is that when the macro runs, it returns the time in more than one row and overwrites the previous timestamp. It starts in row 17, and will record the first time in 17 and 18. When the macro is run again, the time will be recorded in 18 and 19. When it's run a third time, the timestamp is recorded in 18, 19, and 20. So essentially, I'm losing all of my previously recorded data. When I finish, all I have left is the timestamp in row 17 and whatever the last time recorded is.