Make a weekday calculator in VBScript

This is another hta file which will tell you the weekday of the date you specified. The code is a little complex so when I looked at the code after making this, even I had difficulty in understanding the code. I took the formula from the internet and this program is tested so you can be hundred percent sure this program is accurate.

To make the program just save the following code with a .hta file extension using notepad.

<html>
<head>
<title>WeekDay</title>
<HTA:APPLICATION
  APPLICATIONNAME="WeekDay"
  ID="WeekDay"
  VERSION="1.0"
  MAXIMIZEBUTTON="no"
  SCROLL="no"/>
</head>

<script language="VBScript">

Sub Window_OnLoad
   Dim width,height
   width=260
   height=165
   self.ResizeTo width,height
  'This method will be called when the application loads
  'Add your code here
End Sub

Function Validate
On Error Resume Next
CY = CYear.Value
CM = CMonth.value
CD = CDay.value
Chk = Int(CY/4)
If (CY = "") Then
Box.Value = "Enter a year!"
Else If Not (IsNumeric(CY)) Then
Box.Value = "Invalid date!"
Else If (CY < 1000 Or CY > 9999) Then
Box.Value = "Invalid date!"
Else If ((CM = "February" Or CM = "April" Or CM = "June" Or CM = "September" Or CM = "November") And CD = 31) Then
Box.Value = "Invalid date!"
Else If (CM = "February" And CD = 30) Then
Box.Value = "Invalid date!"
Else If (CM = "February" And CD = 29 And Chk*4 <> Int(CY)) Then
Box.Value = "Invalid date!"
Else
IA()
End If
End If
End If
End If
End If
End If
End Function

Function IA
CY = CYear.Value
CC = Left(CY, 2)
CHK = CC Mod 4
If (CHK = 3) Then
XC.Value = 0
NUM.Value = 0
IB()
Else If (CHK = 0) Then
XC.Value = 6
NUM.Value = 0
IB()
Else If (CHK = 1) Then
XC.Value = 4
NUM.Value = 0
IB()
Else If (CHK = 2) Then
XC.Value = 2
NUM.Value = 0
IB()
Else
MsgBox("ERROR!")
End If
End If
End If
End If
End Function

Function IB
CY = Int(CYear.Value)
CC = Int(Right(CY, 2))
NUM.Value = NUM.Value+1
CHK = NUM.Value*4
If (Int(CHK) < Int(CC)) Then
Junk = SetTimeOut("IB()", 1)
Else If (Int(CHK) = Int(CC)) Then
XY.Value = (CC+NUM.Value)
IC()
Else If (Int(CHK) > Int(CC)) Then
XY.Value = (CC+(NUM.Value-1))
IC()
Else
IC()
End If
End If
End If
End Function

Function IC
CY = Right(CYear.Value, 2)
CM = CMonth.Value
Chk = CY Mod 4
If (CY = 0)  Then
XY.Value = 0
ID()
Else If (Chk = 0 And (CM = "January" Or CM = "February")) Then
XY.Value = (XY.Value-1) Mod 7
ID()
Else
XY.Value = XY.Value Mod 7
ID()
End If
End If
End Function

Function ID
IDM = Array(0, 3, 3, 6, 1, 4, 6, 2, 5, 0, 3, 5)
XM.Value = IDM(CMonth.selectedIndex)
CD = CDay.Value
XD.Value = CD Mod 7
Finish()
End Function

Function Finish
DDay = Array("Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday")
Chk = Int(XC.Value)+Int(XY.Value)+Int(XM.Value)+Int(XD.Value)
Box.Value = (DDay(Chk Mod 7))
End Function

Sub CYear_OnKeyPress
If (window.event.keycode < 48 Or window.event.keycode > 57) Then
window.event.returnvalue = False
Else
End If
End Sub

</script>

<body bgcolor="white">
<input type="hidden" id="NUM">
<input type="hidden" id="XC">
<input type="hidden" id="XY">
<input type="hidden" id="XM">
<input type="hidden" id="XD">
<table align="center" width="200" border="1">
<tr>
<td align="center"><input type="text" id="box" size="30" style="text-align:center" maxlength="0"></td>
</tr>
<tr>
<td align="center">
<select id="CDay">
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
<option value="5">5</option>
<option value="6">6</option>
<option value="7">7</option>
<option value="8">8</option>
<option value="9">9</option>
<option value="10">10</option>
<option value="11">11</option>
<option value="12">12</option>
<option value="13">13</option>
<option value="14">14</option>
<option value="15">15</option>
<option value="16">16</option>
<option value="17">17</option>
<option value="18">18</option>
<option value="19">19</option>
<option value="20">20</option>
<option value="21">21</option>
<option value="22">22</option>
<option value="23">23</option>
<option value="24">24</option>
<option value="25">25</option>
<option value="26">26</option>
<option value="27">27</option>
<option value="28">28</option>
<option value="29">29</option>
<option value="30">30</option>
<option value="31">31</option>
</select>
<select id="CMonth">
<option value="January">January</option>
<option value="February">February</option>
<option value="March">March</option>
<option value="April">April</option>
<option value="May">May</option>
<option value="June">June</option>
<option value="July">July</option>
<option value="August">August</option>
<option value="September">September</option>
<option value="October">October</option>
<option value="November">November</option>
<option value="December">December</option>
</select>
<input type="text" id="CYear" size="2" maxlength="4"></td>
</tr>
<tr>
<td align="center"><input type="button" value="Calculate" onClick="Validate"></td>
</tr>
</table>
</body>
</html>

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