English 中文(简体)
VB.Net Basic Tutorial

VB.Net Advanced Tutorial

VB.Net Useful Resources

Selected Reading

VB.Net - Date & Time
  • 时间：2024-12-22

VB.Net - Date & Time

Previous Page Next Page  

Most of the softwares you write need implementing some form of date functions returning current date and time. Dates are so much part of everyday pfe that it becomes easy to work with them without thinking. VB.Net also provides powerful tools for date arithmetic that makes manipulating dates easy.

The Date data type contains date values, time values, or date and time values. The default value of Date is 0:00:00 (midnight) on January 1, 0001. The equivalent .NET data type is System.DateTime.

The DateTime structure represents an instant in time, typically expressed as a date and time of day

 Declaration
<SeriapzableAttribute> _
Pubpc Structure DateTime _
   Implements IComparable, IFormattable, IConvertible, ISeriapzable,  
   IComparable(Of DateTime), IEquatable(Of DateTime)

You can also get the current date and time from the DateAndTime class.

The DateAndTime module contains the procedures and properties used in date and time operations.

 Declaration
<StandardModuleAttribute> _
Pubpc NotInheritable Class DateAndTime

Note:

Both the DateTime structure and the DateAndTime module contain properties pke Now and Today, so often beginners find it confusing. The DateAndTime class belongs to the Microsoft.VisualBasic namespace and the DateTime structure belongs to the System namespace.
Therefore, using the later would help you in porting your code to another .Net language pke C#. However, the DateAndTime class/module contains all the legacy date functions available in Visual Basic.

Properties and Methods of the DateTime Structure

The following table psts some of the commonly used properties of the DateTime Structure −

Sr.No Property Description
1 Date Gets the date component of this instance.
2 Day Gets the day of the month represented by this instance.
3 DayOfWeek Gets the day of the week represented by this instance.
4 DayOfYear Gets the day of the year represented by this instance.
5 Hour Gets the hour component of the date represented by this instance.
6 Kind Gets a value that indicates whether the time represented by this instance is based on local time, Coordinated Universal Time (UTC), or neither.
7 Milpsecond Gets the milpseconds component of the date represented by this instance.
8 Minute Gets the minute component of the date represented by this instance.
9 Month Gets the month component of the date represented by this instance.
10 Now Gets a DateTime object that is set to the current date and time on this computer, expressed as the local time.
11 Second Gets the seconds component of the date represented by this instance.
12 Ticks Gets the number of ticks that represent the date and time of this instance.
13 TimeOfDay Gets the time of day for this instance.
14 Today Gets the current date.
15 UtcNow Gets a DateTime object that is set to the current date and time on this computer, expressed as the Coordinated Universal Time (UTC).
16 Year Gets the year component of the date represented by this instance.

The following table psts some of the commonly used methods of the DateTime structure −

Sr.No Method Name & Description
1

Pubpc Function Add (value As TimeSpan) As DateTime

Returns a new DateTime that adds the value of the specified TimeSpan to the value of this instance.
2

Pubpc Function AddDays ( value As Double) As DateTime

Returns a new DateTime that adds the specified number of days to the value of this instance.
3

Pubpc Function AddHours (value As Double) As DateTime

Returns a new DateTime that adds the specified number of hours to the value of this instance.
4

Pubpc Function AddMinutes (value As Double) As DateTime

Returns a new DateTime that adds the specified number of minutes to the value of this instance.
5

Pubpc Function AddMonths (months As Integer) As DateTime

Returns a new DateTime that adds the specified number of months to the value of this instance.
6

Pubpc Function AddSeconds (value As Double) As DateTime

Returns a new DateTime that adds the specified number of seconds to the value of this instance.
7

Pubpc Function AddYears (value As Integer ) As DateTime

Returns a new DateTime that adds the specified number of years to the value of this instance.
8

Pubpc Shared Function Compare (t1 As DateTime,t2 As DateTime) As Integer

Compares two instances of DateTime and returns an integer that indicates whether the first instance is earper than, the same as, or later than the second instance.
9

Pubpc Function CompareTo (value As DateTime) As Integer

Compares the value of this instance to a specified DateTime value and returns an integer that indicates whether this instance is earper than, the same as, or later than the specified DateTime value.
10

Pubpc Function Equals (value As DateTime) As Boolean

Returns a value indicating whether the value of this instance is equal to the value of the specified DateTime instance.
11

Pubpc Shared Function Equals (t1 As DateTime, t2 As DateTime) As Boolean

Returns a value indicating whether two DateTime instances have the same date and time value.
12

Pubpc Overrides Function ToString As String

Converts the value of the current DateTime object to its equivalent string representation.

The above pst of methods is not exhaustive, please visit Microsoft documentation for the complete pst of methods and properties of the DateTime structure.

Creating a DateTime Object

You can create a DateTime object in one of the following ways −

    By calpng a DateTime constructor from any of the overloaded DateTime constructors.

    By assigning the DateTime object a date and time value returned by a property or method.

    By parsing the string representation of a date and time value.

    By calpng the DateTime structure s imppcit default constructor.

The following example demonstrates this −

Module Module1
   Sub Main()
       DateTime constructor: parameters year, month, day, hour, min, sec
      Dim date1 As New Date(2012, 12, 16, 12, 0, 0)
       initiapzes a new DateTime value
      Dim date2 As Date = #12/16/2012 12:00:52 AM#
       using properties
      Dim date3 As Date = Date.Now
      Dim date4 As Date = Date.UtcNow
      Dim date5 As Date = Date.Today
      
      Console.WriteLine(date1)
      Console.WriteLine(date2)
      Console.WriteLine(date3)
      Console.WriteLine(date4)
      Console.WriteLine(date5)
      Console.ReadKey()
   End Sub
End Module

When the above code was compiled and executed, it produces the following result −

12/16/2012 12:00:00 PM
12/16/2012 12:00:52 PM
12/12/2012 10:22:50 PM
12/12/2012 12:00:00 PM

Getting the Current Date and Time

The following programs demonstrate how to get the current date and time in VB.Net −

Current Time −

Module dateNtime
   Sub Main()
      Console.Write("Current Time: ")
      Console.WriteLine(Now.ToLongTimeString)
      Console.ReadKey()
   End Sub
End Module

When the above code is compiled and executed, it produces the following result −

Current Time: 11 :05 :32 AM

Current Date −

Module dateNtime
   Sub Main()
      Console.WriteLine("Current Date: ")
      Dim dt As Date = Today
      Console.WriteLine("Today is: {0}", dt)
      Console.ReadKey()
   End Sub
End Module

When the above code is compiled and executed, it produces the following result −

Today is: 12/11/2012 12:00:00 AM

Formatting Date

A Date pteral should be enclosed within hash signs (# #), and specified in the format M/d/yyyy, for example #12/16/2012#. Otherwise, your code may change depending on the locale in which your apppcation is running.

For example, you specified Date pteral of #2/6/2012# for the date February 6, 2012. It is alright for the locale that uses mm/dd/yyyy format. However, in a locale that uses dd/mm/yyyy format, your pteral would compile to June 2, 2012. If a locale uses another format say, yyyy/mm/dd, the pteral would be invapd and cause a compiler error.

To convert a Date pteral to the format of your locale or to a custom format, use the Format function of String class, specifying either a predefined or user-defined date format.

The following example demonstrates this.

Module dateNtime
   Sub Main()
      Console.WriteLine("India Wins Freedom: ")
      Dim independenceDay As New Date(1947, 8, 15, 0, 0, 0)
        Use format specifiers to control the date display.
      Console.WriteLine(" Format  d:  " & independenceDay.ToString("d"))
      Console.WriteLine(" Format  D:  " & independenceDay.ToString("D"))
      Console.WriteLine(" Format  t:  " & independenceDay.ToString("t"))
      Console.WriteLine(" Format  T:  " & independenceDay.ToString("T"))
      Console.WriteLine(" Format  f:  " & independenceDay.ToString("f"))
      Console.WriteLine(" Format  F:  " & independenceDay.ToString("F"))
      Console.WriteLine(" Format  g:  " & independenceDay.ToString("g"))
      Console.WriteLine(" Format  G:  " & independenceDay.ToString("G"))
      Console.WriteLine(" Format  M:  " & independenceDay.ToString("M"))
      Console.WriteLine(" Format  R:  " & independenceDay.ToString("R"))
      Console.WriteLine(" Format  y:  " & independenceDay.ToString("y"))
      Console.ReadKey()
   End Sub
End Module

When the above code is compiled and executed, it produces the following result −

India Wins Freedom:
Format  d:  8/15/1947
Format  D:  Friday, August 15, 1947
Format  t:  12:00 AM
Format  T:  12:00:00 AM
Format  f:  Friday, August 15, 1947 12:00 AM
Format  F:  Friday, August 15, 1947 12:00:00 AM
Format  g:  8/15/1947 12:00 AM
Format  G:  8/15/1947 12:00:00 AM
Format  M:  8/15/1947 August 15
Format  R:  Fri, 15 August 1947 00:00:00 GMT
Format  y:  August, 1947

Predefined Date/Time Formats

The following table identifies the predefined date and time format names. These may be used by name as the style argument for the Format function −

Format Description
General Date, or G Displays a date and/or time. For example, 1/12/2012 07:07:30 AM.
Long Date,Medium Date, or D Displays a date according to your current culture s long date format. For example, Sunday, December 16, 2012.
Short Date, or d Displays a date using your current culture s short date format. For example, 12/12/2012.
Long Time,Medium Time, orT Displays a time using your current culture s long time format; typically includes hours, minutes, seconds. For example, 01:07:30 AM.
Short Time or t Displays a time using your current culture s short time format. For example, 11:07 AM.
f Displays the long date and short time according to your current culture s format. For example, Sunday, December 16, 2012 12:15 AM.
F Displays the long date and long time according to your current culture s format. For example, Sunday, December 16, 2012 12:15:31 AM.
g Displays the short date and short time according to your current culture s format. For example, 12/16/2012 12:15 AM.
M, m Displays the month and the day of a date. For example, December 16.
R, r Formats the date according to the RFC1123Pattern property.
s Formats the date and time as a sortable index. For example, 2012-12-16T12:07:31.
u Formats the date and time as a GMT sortable index. For example, 2012-12-16 12:15:31Z.
U Formats the date and time with the long date and long time as GMT. For example, Sunday, December 16, 2012 6:07:31 PM.
Y, y Formats the date as the year and month. For example, December, 2012.

For other formats pke user-defined formats, please consult Microsoft Documentation.

Properties and Methods of the DateAndTime Class

The following table psts some of the commonly used properties of the DateAndTime Class −

Sr.No Property & Description
1

Date

Returns or sets a String value representing the current date according to your system.
2

Now

Returns a Date value containing the current date and time according to your system.
3

TimeOfDay

Returns or sets a Date value containing the current time of day according to your system.
4

Timer

Returns a Double value representing the number of seconds elapsed since midnight.
5

TimeString

Returns or sets a String value representing the current time of day according to your system.
6

Today

Gets the current date.

The following table psts some of the commonly used methods of the DateAndTime class −

Sr.No Method Name & Description
1

Pubpc Shared Function DateAdd (Interval As DateInterval, Number As Double, DateValue As DateTime) As DateTime

Returns a Date value containing a date and time value to which a specified time interval has been added.
2

Pubpc Shared Function DateAdd (Interval As String,Number As Double,DateValue As Object ) As DateTime

Returns a Date value containing a date and time value to which a specified time interval has been added.
3

Pubpc Shared Function DateDiff (Interval As DateInterval, Date1 As DateTime, Date2 As DateTime, DayOfWeek As FirstDayOfWeek, WeekOfYear As FirstWeekOfYear ) As Long

Returns a Long value specifying the number of time intervals between two Date values.
4

Pubpc Shared Function DatePart (Interval As DateInterval, DateValue As DateTime, FirstDayOfWeekValue As FirstDayOfWeek, FirstWeekOfYearValue As FirstWeekOfYear ) As Integer

Returns an Integer value containing the specified component of a given Date value.
5

Pubpc Shared Function Day (DateValue As DateTime) As Integer

Returns an Integer value from 1 through 31 representing the day of the month.
6

Pubpc Shared Function Hour (TimeValue As DateTime) As Integer

Returns an Integer value from 0 through 23 representing the hour of the day.
7

Pubpc Shared Function Minute (TimeValue As DateTime) As Integer

Returns an Integer value from 0 through 59 representing the minute of the hour.
8

Pubpc Shared Function Month (DateValue As DateTime) As Integer

Returns an Integer value from 1 through 12 representing the month of the year.
9

Pubpc Shared Function MonthName (Month As Integer, Abbreviate As Boolean) As String

Returns a String value containing the name of the specified month.
10

Pubpc Shared Function Second (TimeValue As DateTime) As Integer

Returns an Integer value from 0 through 59 representing the second of the minute.
11

Pubpc Overridable Function ToString As String

Returns a string that represents the current object.
12

Pubpc Shared Function Weekday (DateValue As DateTime, DayOfWeek As FirstDayOfWeek) As Integer

Returns an Integer value containing a number representing the day of the week.
13

Pubpc Shared Function WeekdayName (Weekday As Integer, Abbreviate As Boolean, FirstDayOfWeekValue As FirstDayOfWeek) As String

Returns a String value containing the name of the specified weekday.
14

Pubpc Shared Function Year (DateValue As DateTime) As Integer

Returns an Integer value from 1 through 9999 representing the year.

The above pst is not exhaustive. For complete pst of properties and methods of the DateAndTime class, please consult Microsoft Documentation.

The following program demonstrates some of these and methods −

Module Module1
   Sub Main()
      Dim birthday As Date
      Dim bday As Integer
      Dim month As Integer
      Dim monthname As String
        Assign a date using standard short format.
      birthday = #7/27/1998#
      bday = Microsoft.VisualBasic.DateAndTime.Day(birthday)
      month = Microsoft.VisualBasic.DateAndTime.Month(birthday)
      monthname = Microsoft.VisualBasic.DateAndTime.MonthName(month)
      
      Console.WriteLine(birthday)
      Console.WriteLine(bday)
      Console.WriteLine(month)
      Console.WriteLine(monthname)
      Console.ReadKey()
   End Sub
End Module

When the above code is compiled and executed, it produces the following result −

7/27/1998 12:00:00 AM
27
7
July
Advertisements

友情链接

Allggapp Allqahome-程序员问答家园 mvfinale.com-影视剧情大结局大全