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DatePart Function (Visual Basic) 

Returns an Integer value containing the specified component of a given Date value.


Public Overloads Function DatePart( _
   ByVal Interval As DateInterval, _
   ByVal DateValue As DateTime, _
   Optional ByVal FirstDayOfWeekValue As FirstDayOfWeek = VbSunday, _
   Optional ByVal FirstWeekOfYearValue As FirstWeekOfYear = VbFirstJan1 _
) As Integer
' -or-
Public Overloads Function DatePart( _
    ByVal Interval As String, _
   ByVal DateValue As Object, _
   Optional ByVal DayOfWeek As FirstDayOfWeek = FirstDayOfWeek.Sunday, _
   Optional ByVal WeekOfYear As FirstWeekOfYear = FirstWeekOfYear.Jan1 _
) As Integer

Parameters

Interval

Required. DateInterval enumeration value or String expression representing the part of the date/time value you want to return.

DateValue

Required. Date value that you want to evaluate.

FirstDayOfWeekValue, DayOfWeek

Optional. A value chosen from the FirstDayOfWeek enumeration that specifies the first day of the week. If not specified, FirstDayOfWeek.Sunday is used.

FirstWeekOfYearValue, WeekOfYear

Optional. A value chosen from the FirstWeekOfYear enumeration that specifies the first week of the year. If not specified, FirstWeekOfYear.Jan1 is used.

The Interval argument can have one of the following settings.

Enumeration value String Part of date/time value to return

DateInterval.Day

d

Day of month (1 through 31)

DateInterval.DayOfYear

y

Day of year (1 through 366)

DateInterval.Hour

h

Hour

DateInterval.Minute

n

Minute

DateInterval.Month

m

Month

DateInterval.Quarter

q

Quarter

DateInterval.Second

s

Second

DateInterval.Weekday

w

Day of week (1 through 7)

DateInterval.WeekOfYear

ww

Week of year (1 through 53)

DateInterval.Year

yyyy

Year

The FirstDayOfWeekValue argument can have one of the following settings.

Enumeration value Value Description

FirstDayOfWeek.System

0

First day of week specified in system settings

FirstDayOfWeek.Sunday

1

Sunday (default)

FirstDayOfWeek.Monday

2

Monday (complies with ISO standard 8601, section 3.17)

FirstDayOfWeek.Tuesday

3

Tuesday

FirstDayOfWeek.Wednesday

4

Wednesday

FirstDayOfWeek.Thursday

5

Thursday

FirstDayOfWeek.Friday

6

Friday

FirstDayOfWeek.Saturday

7

Saturday

The FirstWeekOfYearValue argument can have one of the following settings.

Enumeration value Value Description

FirstWeekOfYear.System

0

First week of year specified in system settings

FirstWeekOfYear.Jan1

1

Week in which January 1 occurs (default)

FirstWeekOfYear.FirstFourDays

2

Week that has at least four days in the new year (complies with ISO standard 8601, section 3.17)

FirstWeekOfYear.FirstFullWeek

3

First full week in new year

Exception type Error number Condition

ArgumentException

5

Interval is invalid.

InvalidCastException

13

DateValue is not coercible to Date.

See the "Error number" column if you are upgrading Visual Basic 6.0 applications that use unstructured error handling. (You can compare the error number against the Number Property (Err Object).) However, when possible, you should consider replacing such error control with Structured Exception Handling Overview for Visual Basic.

You can use the DatePart function to evaluate a date/time value and return a specific component. For example, you might use DatePart to calculate the day of the week or the current hour.

If you choose DateInterval.Weekday for the Interval argument, the returned value is consistent with the values of the FirstDayOfWeek enumeration. If you choose DateInterval.WeekOfYear, DatePart uses the Calendar and CultureInfo classes of the System.Globalization namespace to determine your current settings.

The FirstDayOfWeekValue argument affects calculations that use the DateInterval.Weekday and DateInterval.WeekOfYear Interval settings. The FirstWeekOfYearValue argument affects calculations that specify DateInterval.WeekOfYear for Interval.

Since every Date value is supported by a DateTime structure, its methods give you additional options in retrieving date/time parts. For example, you can obtain the entire date value of a Date variable, with the time value set to midnight, as follows:

Dim CurrDatTim As Date = Now   ' Current date and time.
Dim LastMidnight As Date = CurrDatTim.Date   ' At midnight.

This example takes a date and, using the DatePart function, displays the quarter of the year in which it occurs.

Dim FirstDate, Msg As String   'Declare variables.
Dim SecondDate As Date
FirstDate = InputBox("Enter a date:")
SecondDate = CDate(FirstDate)
Msg = "Quarter: " & DatePart(DateInterval.Quarter, SecondDate)
MsgBox(Msg)

Namespace: Microsoft.VisualBasic

Module: DateAndTime

Assembly: Visual Basic Runtime Library (in Microsoft.VisualBasic.dll)

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