# Cheap And Reliable Hosting :: How To Convert Date From Solar to Lunar (Hijri) Using VB.NET

Today I will explain about how to convert date from solar to lunar (Hijri) Using VB.NET The Lunar (Hijri) calendar is very important for Muslims as is the Solar calendar is important because the Lunar calendar was related to some elements of worship, so I looked at many sites on the internet to understand how to calculate the age of the moon in any given day, I found many sites offering various ways and I took what I found to provide results closer to the truth.

I’ve noticed that most sites agree on the expense of the date but don’t agree on how to calculate the age of the moon and found the difference between these sites to be up to one day and when the moon’s age is 30 days, the result is zero in some sites.
In this program I calculate the approximate age of the moon in days and did not give attention to the parts of the day of the hours and minutes.

For the program to be more useful, I added a PictureBox control to display the lighted part of the moon and darkness part of the moon commensurate with the age of the moon.
There is a small probability of a one-day error for any calculation to convert a date. Note: You can read Months by its name or by its number.

## Code

### Best Calculation to Get Number Approximation

```Private Function getInt(ByRef fNumber As Double) As Double
If fNumber < -0.0000001 Then
getInt = Math.Ceiling(fNumber - 0.0000001)
Else
getInt = Math.Floor(fNumber + 0.0000001)
End If
End Function```

### Convert Solar Date to Lunar (Hijri) Date

```Private Sub SolarToLunar()
' convert Solar year from 622 to 2500
Dim jd As Double
Dim j, L, n As Double
Dim d, m, y As Integer
Dim theDay As Integer
' Solar day
d = Val(SolarDay.Text)
'get the number of Solar month
m = SolarMonth.SelectedIndex + 1
' Solar year
y = Val(SolarYear.Text)
If (y > 1582) Or ((y = 1582) And (m > 10)) Or ((y = 1582) And (m = 10) And (d > 14)) Then
jd = getInt((1461 * (y + 4800 + getInt((m - 14) / 12))) / 4) + getInt((367 * (m - 2 - 12 * (getInt((m - 14) / 12)))) / 12) - getInt((3 * (getInt((y + 4900 + getInt((m - 14) / 12)) / 100))) / 4) + d - 32075
Else
jd = 367 * y - getInt((7 * (y + 5001 + getInt((m - 9) / 7))) / 4) + getInt((275 * m) / 9) + d + 1729777
End If
' Solar year >= 622
If jd < 1948440 Then
DateMinError()
Exit Sub
End If
' Solar year <= 2500
If jd > 2621734 Then
DateMaxError()
Exit Sub
End If
'day of the week
theDay = jd Mod 7
lblDay.Text = WeekDays(theDay)
L = jd - 1948440 + 10632
n = getInt((L - 1) / 10631)
L = L - 10631 * n + 354
j = (getInt((10985 - L) / 5316)) * (getInt((50 * L) / 17719)) + (getInt(L / 5670)) * (getInt((43 * L) / 15238))
L = L - (getInt((30 - j) / 15)) * (getInt((17719 * j) / 50)) - (getInt(j / 16)) * (getInt((15238 * j) / 43)) + 29
m = Int(getInt((24 * L) / 709))
d = Int(L - getInt((709 * m) / 24))
y = Int(30 * n + j - 30)
' display Lunar date
LunarDay.Text = Str(d)
LunarMonth.Text = LunarMonths(m - 1)
LunarYear.Text = Str(y)
ShowMoonPhase()
If d = 1 Then
lblAge.Text = Str(d) & " day"
Else
lblAge.Text = Str(d) & " days"
End If
End Sub  ```

### Convert Lunar (Hijri) Date to Solar Date

```Private Sub LunarToSolar()
' convert Lunar year from 1 to 1900
Dim jd As Double
Dim i, j, k, L, n As Double
Dim d, m, y As Integer
Dim theDay As Integer
' Lunar day
d = Val(LunarDay.Text)
If d = 1 Then
lblAge.Text = Str(d) & " day"
Else
lblAge.Text = Str(d) & " days"
End If
'get the number of Lunar month
m = LunarMonth.SelectedIndex + 1
' Lunar year
y = Val(LunarYear.Text)
jd = getInt((11 * y + 3) / 30) + 354 * y + 30 * m - getInt((m - 1) / 2) + d + 1948440 - 385
'day of the week
theDay = jd Mod 7
lblDay.Text = WeekDays(theDay)
If jd > 2299160 Then
L = jd + 68569
n = getInt((4 * L) / 146097)
L = L - getInt((146097 * n + 3) / 4)
i = getInt((4000 * (L + 1)) / 1461001)
L = L - getInt((1461 * i) / 4) + 31
j = getInt((80 * L) / 2447)
d = Int(L - getInt((2447 * j) / 80))
L = getInt(j / 11)
m = Int(j + 2 - 12 * L)
y = Int(100 * (n - 49) + i + L)
Else
j = jd + 1402
k = getInt((j - 1) / 1461)
L = j - 1461 * k
n = getInt((L - 1) / 365) - getInt(L / 1461)
i = L - 365 * n + 30
j = getInt((80 * i) / 2447)
d = Int(i - getInt((2447 * j) / 80))
i = getInt(j / 11)
m = Int(j + 2 - 12 * i)
y = Int(4 * k + n + i - 4716)
End If
' display Solar date
SolarDay.Text = Str(d)
SolarMonth.Text = SolarMonths(m - 1)
SolarYear.Text = Str(y)
ShowMoonPhase()
End Sub  ```

### Draw the Moon at Selected Date

```Private Sub ShowMoonPhase()
Dim ag As Integer = Val(LunarDay.Text)
Dim Phase As Double = ag / 29.530588853
Dim Xpos, Ypos, Rpos As Integer
Dim Xpos1, Xpos2 As Integer
Me.ClearDraw() 'clear PicMoon PictureBox
' Width of 'ImageToDraw' Object = Width of 'PicMoon' control
Dim PageWidth As Integer = Me.MoonShape.Width
' Height of 'ImageToDraw' Object = Height of 'PicMoon' control
Dim PageHeight As Integer = Me.MoonShape.Height
' Initiate 'ImageToDraw' Object with size = size of control 'PicMoon' control
Dim ImageToDraw As Bitmap = New Bitmap(PageWidth, PageHeight)
'Create graphics object for alteration.
Dim newGraphics As Graphics = Graphics.FromImage(ImageToDraw)
Dim PenW As Pen = New Pen(Color.White) ' For lighted part of the moon
Dim PenB As Pen = New Pen(Color.Black) ' For darkness part of the moon
For Ypos = 0 To 45
Xpos = Int(Math.Sqrt(45 * 45 - Ypos * Ypos))
' Draw darkness part of the moon
Dim pB1 As Point = New Point(90 - Xpos, Ypos + 90)
Dim pB2 As Point = New Point(Xpos + 90, Ypos + 90)
Dim pB3 As Point = New Point(90 - Xpos, 90 - Ypos)
Dim pB4 As Point = New Point(Xpos + 90, 90 - Ypos)
newGraphics.DrawLine(PenW, pB1, pB2)
newGraphics.DrawLine(PenW, pB3, pB4)
' Determine the edges of the lighted part of the moon
Rpos = 2 * Xpos
If (Phase < 0.5) Then
Xpos1 = -Xpos
Xpos2 = Int(Rpos - 2 * Phase * Rpos - Xpos)
Else
Xpos1 = Xpos
Xpos2 = Int(Xpos - 2 * Phase * Rpos + Rpos)
End If
' Draw the lighted part of the moon
Dim pW1 As Point = New Point(Xpos1 + 90, 90 - Ypos)
Dim pW2 As Point = New Point(Xpos2 + 90, 90 - Ypos)
Dim pW3 As Point = New Point(Xpos1 + 90, Ypos + 90)
Dim pW4 As Point = New Point(Xpos2 + 90, Ypos + 90)
newGraphics.DrawLine(PenB, pW1, pW2)
newGraphics.DrawLine(PenB, pW3, pW4)
Next
' Display the bitmap in the picture box.
Me.MoonShape.Image = ImageToDraw
' Release graphics object
PenW.Dispose()
PenB.Dispose()
newGraphics.Dispose()
ImageToDraw = Nothing
End Sub  ```