DateDiff

• Source: https://www.freebasic.net/wiki/wikka.php?wakka=KeyPgDateDiff
• Last revised: 2022-03-25

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Gets the difference of two dates measured by a specified interval

Syntax

` declare function DateDiff ( byref interval as const string, byval serial1 as double, byval serial2 as double, byval firstdayofweek as long = fbUseSystem, byval firstdayofyear as long = fbUseSystem ) as longint

`

Usage

#include "vbcompat.bi"
result = DateDiff( interval, date_serial1, date_serial2 [, firstdayofWeek [, firstweekofyear ] ] )

Parameters

interval

the unit of time (interval) with which to measure the difference

date_serial1

starting date serial

date_serial2

end date serial

firstdayofweek

first day of the week

firstdayofyear

first day of the year

Return Value

Returns a longint corresponding to the number of intervals found between two Date Serials.

If date_serial1 > date_serial2, the result is negative.

Description

interval is specified as follows:

value	interval
yyyy	years
q	quarter(three months)
m	months
w	seven day periods
ww	calendar weeks
d,y	days
h	hours
n	minutes
s	seconds

first_dayofweek Affects the counting when 'ww' interval is used.

value	first day of week	constant
omitted	sunday
0	local settings	fbUseSystem
1	sunday	fbSunday
2	monday	fbMonday
3	tuesday	fbTuesday
4	wednesday	fbWednesday
5	thursday	fbThursday
6	friday	fbFriday
7	saturday	fbSaturday

first_weekofyear specifies which year (previous or next) that the week which spans the end of one year and the beginning of the next should included with.

value	first week of year	constant
0	local settings	fbUseSystem
1	January 1's week	fbFirstJan1
2	first weeks having 4 days in the year	fbFirstFourDays
3	first full week of year	fbFirstFullWeek

Notice if you do an arithmetical subtraction of two date serials you get the difference in days.

The compiler will not recognize this function unless vbcompat.bi or datetime.bi is included.

Examples

start GeSHi

#include "vbcompat.bi"

Dim s As String, d1 As Double, d2 As Double

Line Input "Enter your birthday: ", s

If IsDate( s ) Then
  d1 = DateValue( s )
  d2 = Now()

  Print "You are " & DateDiff( "yyyy", d1, d2 ) & " years old."
  Print "You are " & DateDiff( "d", d1, d2 ) & " days old."
  Print "You are " & DateDiff( "s", d1, d2 ) & " seconds old."

Else
  Print "Invalid date"

End If

end GeSHi

Differences from QB

• Did not exist in QB. This function appeared in Visual Basic.

See also

• Date Serials

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