ACC: Functions for Calculating and Displaying Date/Time Values (88657)

MORE INFORMATION

Displaying Specific Dates

To display specific dates, you can use the DateSerial() function to manipulate the day, month, and year portions of a date. For example, you can use the following expressions in the ControlSource property of a text box or in the Debug window (or the Immediate window in versions 1.x and 2.0) to return specific dates:

• The current month:

  DateSerial(Year(Date()), Month(Date()), 1)

• The next month:

  DateSerial(Year(Date()), Month(Date()) + 1, 1)

• The last day of the current month:

  DateSerial(Year(Date()), Month(Date()) + 1, 0)

• The last day of the next month:

  DateSerial(Year(Date()), Month(Date()) + 2, 0)

• The first day of the previous month:

  DateSerial(Year(Date()), Month(Date())-1,1)

• The last day of the previous month:

  DateSerial(Year(Date()), Month(Date()),0)

• The first day of the current quarter:

  DateSerial(Year(Date()), Int((Month(Date()) - 1) / 3) * 3 + 1, 1)

• The last day of the current quarter:

  DateSerial(Year(Date()), Int((Month(Date()) - 1) / 3) * 3 + 4, 0)

• The first day of the current week (assuming Sunday = day 1):

  Date() - WeekDay(Date()) + 1

• The last day of the current week:

  Date() - WeekDay(Date()) + 7

• The first day of the current week (using settings in Options dialog box):

  Date() - WeekDay(Date(), 0) + 1

• The last day of the current week:

  Date() - WeekDay(Date(), 0) + 7

For information about calculating the fiscal year or fiscal month, please see the following article in the Microsoft Knowledge Base:

Calculating Time Intervals

Because a time value is stored as a fraction of a 24-hour day, you may receive incorrect formatting results when you try to add, subtract, multiply or divide time data greater than 24 hours.

For example, if you try to find the number of hours elapsed between two dates by subtracting the values in Visual Basic, you may receive an incorrect number. To demonstrate this, type the following code in the Debug window (or Immediate window in version 2.0) and note that it returns a value of 05:00 hours rather than the correct value of 53:00 hours:

   StartDate=#6/1/93 8:00AM#
   EndDate=#6/3/93 1:00PM#
   ?Format(EndDate-StartDate,"hh:mm")
				

To resolve formatting problems caused by time values greater than 24 hours, you can use the Int() and CSng() functions in Visual Basic to separate a calculated time value into different variables for days, hours, minutes, and seconds. For example, you can include the following code fragment in a custom function to create separate time variables:

   '-------------------------------------------------------------------
   ' This sample code separates a time interval into seven variables for
   ' the following values: days, hours, minutes, seconds, total time in
   ' hours, total time in minutes, and total time in seconds.
   '
   ' The interval argument is flexible; it can be a single value, an
   ' expression, or a field reference.
   '-------------------------------------------------------------------

   Dim totalhours As Long, totalminutes As Long, totalseconds As Long
   Dim days As Long, hours As Long, minutes As Long, seconds As Long
   Dim interval As Variant

   days = Int(CSng(interval))
   totalhours = Int(CSng(interval * 24))
   totalminutes = Int(CSng(interval * 1440))
   totalseconds = Int(CSng(interval * 86400))
   hours = totalhours Mod 24
   minutes = totalminutes Mod 60
   seconds = totalseconds Mod 60
				

You can use the totalhours, totalminutes, and totalseconds variables to display a time value as a single unit of time. The days, hours, minutes, and seconds variables enable you to break down a time value into portions of time. To display time values in different formats, you can concatenate these variables as demonstrated in the following sample functions:

• The GetElapsedDays() function calculates the elapsed time between two date/time values and displays the result in days.
• The GetElapsedTime() function calculates the elapsed time between time values and displays the result in days, hours, minutes, and seconds.
• The GetTimeCardTotal() function sums a field of time values in a table and displays the total in hours and minutes.

GetElapsedDays() Sample Function

To create the GetElapsedDays() function, follow these steps:

1. Open the sample database Northwind.mdb.(or NWIND.MDB in versions 1.x and 2.0).
2. Create a module and type the following line in the Declarations section if it is not already there:

   Option Explicit

3. Type the following function:

         Function GetElapsedDays (interval)
            Dim days As Long
   
            days = Int(CSng(interval))
            GetElapsedDays = days &" Days "
   
         End Function
   						

4. To test this function, create a new query based on the Orders table.
5. In the QBE grid, add the following fields.

   In Microsoft Access version 7.0 and 97:

            Field: ShippedDate
               Show: True
            Field: OrderDate
               Show: True
            Field: ElapsedTime: GetElapsedDays([ShippedDate]-[OrderDate])
               Show: True

   In Microsoft Access versions 1.x and 2.0:

            Field: Shipped Date
               Show: True
            Field: Order Date
               Show: True
            Field: ElapsedTime: GetElapsedDays([Shipped Date]-[Order Date])
               Show: True

6. Run the query. Note that the ElapsedTime column displays the number of days between the ShippedDate field (or Shipped Date in versions 1.x and 2.0) and OrderDate field (or Order Date in versions 1.x and 2.0) for each record in the Orders table.

GetElapsedTime() Sample Function

To create the GetElapsedTime() function, follow these steps:

1. Create a new table with the following structure and save it as TimeLog.

         Table: TimeLog
         -----------------------
         Field Name: StartTime
            Data Type: Date/Time
            Format: General Date
         Field Name: EndTime
            Data Type: Date/Time
            Format: General Date

2. View the TimeLog table in Datasheet view, enter the following three records, and then close the table:

         StartTime                 EndTime
         --------------------------------------------
         5/10/95 4:57:00  PM       5/15/95 2:38:00 AM
         5/11/95 10:17:31 AM       5/24/95 6:05:00 PM
         5/18/95 9:16:43  AM       5/19/95 5:03:00 PM

3. Create a module and type the following line in the Declarations section:

   Option Explicit

4. Enter the following function:
   
   NOTE: In the following sample code, an underscore (_) is used as a line-continuation character. Remove the underscore from the end of the line when re-creating this code in Access Basic.

         Function GetElapsedTime (interval)
            Dim totalhours As Long, totalminutes As Long, totalseconds As _
                 Long
            Dim days As Long, hours As Long, Minutes As Long, Seconds As Long
   
            days = Int(CSng(interval))
            totalhours = Int(CSng(interval * 24))
            totalminutes = Int(CSng(interval * 1440))
            totalseconds = Int(CSng(interval * 86400))
            hours = totalhours Mod 24
            Minutes = totalminutes Mod 60
            Seconds = totalseconds Mod 60
   
         GetElapsedTime = days & " Days " & hours & " Hours " & Minutes & _
         " Minutes " & Seconds & " Seconds "
   
   
         End Function
   						

   NOTE: The GetElapsedTime function requires that you pass it a date and a time.
5. To test this function, create a new report based on the TimeLog table using the AutoReport Wizard.
6. View the report in Design view.
7. Add an unbound text box to the TimeLog table's detail section and set its properties as follows:

         Textbox:
            Name: ElapsedTime
            ControlSource: =GetElapsedTime([EndTime]-[StartTime])
            Width: 3 inches

8. Preview the report. Note that each record displays the total elapsed time in days, hours, minutes, and seconds.

GetTimeCardTotal() Sample Function

To create the GetTimeCardTotal() function, follow these steps:

1. Create a new table with the following structure and save it as TimeCard.

         Table: TimeCard
         -----------------------
         Field Name: Daily Hours
            Data Type: Date/Time
            Format: Short Time

2. View the TimeCard table in Datasheet view, enter the following four records, and then close the table:

   8:15
   7:37
   8:12
   8:03

3. Create a module and type the following line in the Declarations section if it's not already there:

   Option Explicit

4. Type the following function:

         Function GetTimeCardTotal ()
            Dim db As Database, rs As Recordset
            Dim totalhours As Long, totalminutes As Long
            Dim days As Long, hours As Long, minutes As Long
            Dim interval As Variant, j As Integer
   
            Set db = dbengine.workspaces(0).databases(0)
            Set rs = db.OpenRecordset("timecard")
            interval = #12:00:00 AM#
               While Not rs.EOF
                  interval = interval + rs![Daily hours]
                  rs.MoveNext
               Wend
            totalhours = Int(CSng(interval * 24))
            totalminutes = Int(CSng(interval * 1440))
            hours = totalhours Mod 24
            minutes = totalminutes Mod 60
   
         GetTimeCardTotal = totalhours &" hours and " &minutes &" minutes"
   
         End Function
   						

5. To test this function, type the following line in the Debug window (or Immediate window in version 1.x and 2.0), and then press ENTER:

   ? GetTimeCardTotal ()

   Note that the Debug window displays 32 hours and 7 minutes.