General Methods of formatting and Subtracting DateTimes ASP.NET Style

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June 01, 2003

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We recently had a need to figure out how to subtract 7 days from a particular date and store it into a variable. What this turned into was an five day marathon of figuring out different ways of formatting dates using ASP.NET. This might seem a redundant but there are literals thousands of different ways of manipulating dates inside .NET. Here are my 17 ways I found along my adventure. Some people would say "find one way and just use it?". Not us, we decided to make this an adventure and come up with a nice reference guide(for us anyway) if the occasion arises to format dates a certain way. We would suggest for anyone wanting to learn about .NET. Take about a week and just start out doing something with .NET and dig into documentation. If you find something new, learn about it and run with it for awhile. We did![bold]Sample Code[/bold]Contained inside each method are various code samples.- Various Ways of Subtracting Time from a Current Date


'Uses the AddDays method to subtract X number of days
Public Function Date2()
  Dim NewTime as DateTime
  NewTime = DateTime.Now.AddDays(-7)
  Dim s as string = NewTime
  return s
End Function

'Thanks to Paul Czywczynski for this idea
'This probably (In My opinion) Offers the most flexibility found so far
'Change where the MM/dd/yyyy to whatever
'response.write(System.String.Format("{0:d}",NewTime))
'would return just the name of the Day
Function Date3()
  Dim NewTime as DateTime = now.addDays(-7) 
  response.write(System.String.Format("{0:MM/dd/yyyy}",NewTime))
End Function


Function Date4()
Dim NewTime as DateTime
  NewTime = now.addDays(-7) 
  return NewTime.ToString()
End Function

- General Formatting Techniques


'Uses the toLongTimeString method
Public Function Date5()
  Dim NewTime as DateTime
  NewTime = Now()
  return newtime.toLongTimeString()
End Function

'Uses the toShortTimeString method
Public Function Date6()
  Dim NewTime as DateTime
  NewTime = Now()
  return newtime.toShortTimeString()
End Function

'Uses the toLongDateString method
Public Function Date7()
  Dim NewTime as DateTime
  NewTime = Now()
  return newtime.toLongDateString()
End Function

'Uses the toShortDateString method
Public Function Date8()
  Dim NewTime as DateTime
  NewTime = Now()
  return newtime.toShortDatestring()
End Function

- Using FormatDateTime Function


'Uses FormatDateTime function General format
Function Date9()
  Dim NewTime as DateTime
  NewTime = DateTime.Now.Subtract( New TimeSpan(7, 0, 0, 0) )
  return formatdatetime(NewTime, 0)
End Function

'Uses FormatDateTime function LongDate format
Function Date10()
  Dim NewTime as DateTime
  NewTime = DateTime.Now.Subtract( New TimeSpan(7, 0, 0, 0) )
  return formatdatetime(NewTime, 1)
End Function

'Uses FormatDateTime function ShortDate format
Function Date11()
  Dim NewTime as DateTime
  NewTime = DateTime.Now.Subtract( New TimeSpan(7, 0, 0, 0) )
  return formatdatetime(NewTime, 2)
End Function

'Uses FormatDateTime function LongTime format
Function Date12()
  Dim NewTime as DateTime
  NewTime = DateTime.Now.Subtract( New TimeSpan(7, 0, 0, 0) )
  return formatdatetime(NewTime, 3)
End Function

'Uses FormatDateTime function ShortTime format
Function Date13()
  Dim NewTime as DateTime
  NewTime = DateTime.Now.Subtract( New TimeSpan(7, 0, 0, 0) )
  return formatdatetime(NewTime, 4)
End Function

- Display Specific parts of the Date(DAY, MONTH, TIME)


'Bring Back just the name of the Day
Function Date14()
  Dim NewTime as DateTime = now.addDays(-7) 
  dim s as string
  s = (System.String.Format("{0:dddd}",NewTime))
  Return s
End Function

'Returns the Integer of what day of week
Function Date15()
  Dim MyDate as DateTime
  Dim MyWeekDay as Integer
  MyDate = Now.AddDays(-5)
  MyWeekDay = Weekday(MyDate)   
  return MyWeekDay
End Function

'Returns the Month Integer
Function Date16()
  Dim MyDate as DateTime
  Dim MyMonth as Integer
  MyDate = Now.AddDays(-5)
  MyMonth = Month(MyDate)   
  return MyMonth
End Function

'Returns just a formatted string
'This method provides just formatting but 
'Very flexible with not a lot of code
Function Date17()
  Dim MyDate as String
  MyDate = Format(Now(), "yyyy")
  return MyDate
End Function
</script>

[bold]Formatting Dates Reference Guide[/bold]----------------------------------------------------[bold]d[/bold]Short Date[bold]D[/bold]Long Date[bold]f[/bold]Full (long date + short time)[bold]F[/bold]Full (long date + long time)[bold]g[/bold]General (short date + short time)[bold]G[/bold]General (short date + long time)[bold]m, M[/bold]Month/Day Date[bold]r, R[/bold]RFC Standard[bold]s[/bold]Sortable without TimeZone info[bold]t[/bold]Short Time[bold]T[/bold]Long Time[bold]u[/bold]Universal with sort able format[bold]U[/bold]Universal with Full (long date + long time) format[bold]y, Y[/bold]Year/Month Date[bold]*Note:[bold] Some systems will not be able to get dates for 2-digit years of less than 1930.----------------------------------------------------