Gets the difference of two dates measured by a specified interval

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 long

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

the unit of time (interval) with which to measure the difference
starting date serial
end date serial
first day of the week
first day of the year

Return Value:
Returns an integer corresponding to the number of intervals found between two Date Serials.

If date_serial1 > date_serial2, the result is negative.

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 or is included.

#include ""

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."

  Print "Invalid date"

End If

Differences from QB:
See also:
Back to Date and Time Functions
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