Why does _DateDiff() return 0?

Question

My AutoIt script should predict when a process will complete by saying The process will be complete at 3:18:24 PM. But that is not happening. It takes these input values:

1. Starting time
2. Starting percentage
3. Current time
4. Current percentage

It displays:

"The extraction will be complete at 0".

I isolated the problem to _DateDiff(). I thought the first parameter was n for difference in minutes. But it returns 0 when I pass the next two parameters (date values spaced sixty minutes apart). Here's the code:

GUICreate("Completion Time Predictor", 300, 300)
;Here I enter the starting time and percentage
GUICtrlCreateLabel("Enter the start time:", 10, 10, 270, 29)
$StartTime = GUICtrlCreateDate("", 10, 40, 270, 21, $DTS_TIMEFORMAT)
GUICtrlCreateLabel("Enter the start percentage:", 10, 70, 270, 29)
Local $StartPercent = GUICtrlCreateInput("", 10, 100, 270, 21)
;Here I enter the current time and percentage
GUICtrlCreateLabel("Enter the current time:", 10, 130, 270, 29)
$CurrentTime = GUICtrlCreateDate("", 10, 160, 270, 21, $DTS_TIMEFORMAT)
GUICtrlCreateLabel("Enter the current percentage:", 10, 190, 270, 29)
Local $CurrentPercent = GUICtrlCreateInput("", 10, 220, 270, 21)
Local $CTRL_a = GUICtrlCreateButton("Calculate", 10, 260, 280, 21)
GUISetState()
Local $msg
Do
    $msg = GUIGetMsg()
    Select
        Case $msg = $CTRL_a
            $PercentChange = GUICtrlRead($CurrentPercent) - GUICtrlRead($StartPercent)
            ;This seems to be where everything is going wrong
            $ChangePerMinute = $PercentChange / _DateDiff('n', GUICtrlRead($StartTime), GUICtrlRead($CurrentTime))
            $MinutesRemaining = (100 - GUICtrlRead($CurrentPercent)) / $ChangePerMinute
            $EndTime = _DateAdd('n', $MinutesRemaining, GUICtrlRead($CurrentTime))
            MsgBox($MB_OK, "Predicted Completion Time:", "The extraction will be complete at  " & $EndTime)
    EndSelect
Until $msg = $GUI_EVENT_CLOSE

Answer 1

I have no idea what you are doing, but maybe this helps you finding the problem

#include <Date.au3>
#include <DateTimeConstants.au3>
#include <GUIConstantsEx.au3>
#include <MsgBoxConstants.au3>
GUICreate("Completion Time Predictor", 300, 300)
;Here I enter the starting time and percentage
GUICtrlCreateLabel("Enter the start time:", 10, 10, 270, 29)
$StartTime = GUICtrlCreateDate("", 10, 40, 270, 21, $DTS_TIMEFORMAT)
GUICtrlCreateLabel("Enter the start percentage:", 10, 70, 270, 29)
Local $StartPercent = GUICtrlCreateInput("0", 10, 100, 270, 21)
;Here I enter the current time and percentage
GUICtrlCreateLabel("Enter the current time:", 10, 130, 270, 29)
$CurrentTime = GUICtrlCreateDate("", 10, 160, 270, 21, $DTS_TIMEFORMAT)
GUICtrlSetData(-1, _NowCalcDate() & ' ' & @HOUR + 1 & ":" & @MIN & ':' & @SEC)
GUICtrlCreateLabel("Enter the current percentage:", 10, 190, 270, 29)
Local $CurrentPercent = GUICtrlCreateInput("10", 10, 220, 270, 21)
Local $CTRL_a = GUICtrlCreateButton("Calculate", 10, 260, 280, 21)
GUISetState()
Local $msg

Do
    $msg = GUIGetMsg()
    Select
        Case $msg = $CTRL_a
            ConsoleWrite(_NowCalcDate() & ' ' & GUICtrlRead($StartTime) & " " & _NowCalcDate() & ' ' & GUICtrlRead($CurrentTime) & @CRLF)
            $PercentChange = GUICtrlRead($CurrentPercent) - GUICtrlRead($StartPercent)
            ConsoleWrite("% Change: " & $PercentChange & @CRLF)
            ;This seems to be where everything is going wrong
            $diff_min = _DateDiff('n', _NowCalcDate() & ' ' & GUICtrlRead($StartTime), _NowCalcDate() & ' ' & GUICtrlRead($CurrentTime))
            ConsoleWrite("Diff in Min: " & $diff_min & @CRLF)
            $ChangePerMinute = $PercentChange / $diff_min
            ConsoleWrite("Change / min : " & $ChangePerMinute & @CRLF)
            $MinutesRemaining = (100 - GUICtrlRead($CurrentPercent)) / $ChangePerMinute
            ConsoleWrite("MinutesRemaining : " & " " & $MinutesRemaining & @CRLF)
            $EndTime = _DateAdd('n', $MinutesRemaining, _NowCalcDate() & ' ' & GUICtrlRead($CurrentTime))
            MsgBox($MB_OK, "Predicted Completion Time:", "The extraction will be complete at  " & $EndTime)
    EndSelect
Until $msg = $GUI_EVENT_CLOSE