Excel-vba quick start (XIII. Common usage of date)

1. Get system time

There are three common ways to obtain system time ：

1. Date Get the date of the current system time
2. Time Get the hour, minute and second of the current system time
3. Now Get the year, day, hour, minute and second of the current system time

Public Sub main()
  Debug.Print Date ' result ：2022/7/27
  Debug.Print Time ' result ：15:00:25
  Debug.Print Now ' result ：2022/7/27 15:00:25
End Sub

2. More detailed extraction time

1. Extract year from date Year( Time )
2. Extract the month from the date Month( Time )
3. Extract the day from the date Day( Time )
4. When extracted from the date Hour( Time )
5. Extract minutes from the date VBA.Minute( Time )
6. Extract seconds from dates Second( Time )
   
   

Public Sub main()
  Debug.Print Year(Now) ' result ：2022
  Debug.Print Month(Now) ' result ：7
  Debug.Print Day(Now) ' result ：27
  Debug.Print Hour(Now) ' result ：15
  Debug.Print VBA.Minute(Now) ' result ：4
  Debug.Print Second(Now) ' result ：20
End Sub

3. Format display date

The syntax of formatting date display is ：Format( Time , Format ), Common formats are ：

Format	describe
yyyy-mm-dd	Specific date
yyyy year mm month dd Japan	Chinese date
yyyy year mm month dd Japan h:mm:ss	Chinese year month day hour minute second
d-mmm-yy	English month abbreviation
d-mmmm-yy	English month
aaaa	Chinese week
ddd	English week abbreviation
dddd	English week

Example ：

Public Sub main()
  Debug.Print Format(Now, "yyyy-mm-dd") ' result ：2022-07-27
  Debug.Print Format(Now, "yyyy year mm month dd Japan ") ' result ：2022 year 07 month 27 Japan 
  Debug.Print Format(Now, "yyyy year mm month dd Japan  h:mm:ss") ' result ：2022 year 07 month 27 Japan  15:13:31
  Debug.Print Format(Now, "d-mmm-yy") ' result ：27-Jul-22
  Debug.Print Format(Now, "d-mmmm-yy") ' result ：27-July-22
  Debug.Print Format(Now, "aaaa") ' result ： Wednesday 
  Debug.Print Format(Now, "ddd") ' result ：Wed
  Debug.Print Format(Now, "dddd") ' result ：Wednesday
End Sub

3. Date difference calculation

The syntax of date difference calculation is ：DateDiff( Time unit , Time , Time of comparison )：

Public Sub main()
  Debug.Print DateDiff("d", "2022-07-27", "2022-07-28") ' How many days   result ：1
  Debug.Print DateDiff("m", "2022-07-28", "2022-08-28") ' A few months away   result ：1
  Debug.Print DateDiff("yyyy", "2022-07-28", "2023-07-28") ' A few years   result ：1
  Debug.Print DateDiff("q", "2022-07-28", "2022-10-01") ' A few quarters apart   result ：1
  Debug.Print DateDiff("w", "2022-07-28", "2022-08-04") ' The difference is several seven days   result ：1
  Debug.Print DateDiff("h", "2022-07-28 15:00", "2022-07-28 16:00") ' A few hours apart   result ：1
  Debug.Print DateDiff("n", "2022-07-28 15:01", "2022-07-28 15:02") ' A few minutes away   result ：1
  Debug.Print DateDiff("s", "2022-07-28 15:01:00", "2022-07-28 15:01:01") ' A few seconds apart   result ：1
End Sub

4. Date addition and subtraction

The syntax for adding and subtracting dates is ：DateAdd( Company , The time of addition and subtraction , Time ), When the time of addition and subtraction is positive, it is plus , A negative number is minus ：

Public Sub main()
  Debug.Print VBA.DateAdd("d", 10, "2022/07/27 16:00:00") ' Add ten days   result ：2022/8/6 16:00:00
  Debug.Print VBA.DateAdd("m", 10, "2022/07/27 16:00:00") ' Add ten months   result ：2023/5/27 16:00:00
  Debug.Print VBA.DateAdd("yyyy", 10, "2022/07/27 16:00:00")  ' Plus ten years   result ：2032/7/27 16:00:00
  Debug.Print VBA.DateAdd("yyyy", -10, "2022/07/27 16:00:00") ' Minus ten days   result ：2012/7/27 16:00:00
  Debug.Print VBA.DateAdd("h", 10, "2022/07/27 16:00:00") ' Add ten hours   result ：2022/7/28 2:00:00
  Debug.Print VBA.DateAdd("n", 10, "2022/07/27 16:00:00") ' Add ten minutes   result ：2022/7/27 16:10:00
  Debug.Print VBA.DateAdd("s", 10, "2022/07/27 16:00:00") ' Add ten seconds   result ：2022/7/27 16:00:10
End Sub

5. Time serialization

Public Sub main()
  Debug.Print VBA.DateSerial(2022, 7, 27) ' result ：2022/7/27
  Debug.Print VBA.TimeSerial(16, 1, 2) ' result ：16:01:02
End Sub