DateDiff

The DateDiff function returns the number of time intervals between two dates.

Syntax
DateDiff(Interval, Date1, Date2 [, FirstDayOfWeek [, FirstWeekOfYear] ])
Return value
Type	Description
Long	Number of time intervals.
Parameter
Use	Name	Type	Passing	Description
Required	Interval	String	ByVal	See below.
Required	Date1	Double	ByVal	Determines the first date.
Required	Date2	Double	ByVal	Determines the second date.
Optional	FirstDayOfWeek	Variant	ByVal	Determines the first day of the week.
Optional	FirstWeekOfYear	Variant	ByVal	Determines the first week of the year.

Interval determines the time interval to be used to calculate the difference between Date1 and Date2. The following values can be specified for Interval:

Interval	Description
yyyy	Year
q	Quarter
m	Month
y	Day of the year
d	Day
w	Weekday
ww	Week
h	Hour
n	Minute
s	Second

You can use the optional FirstDayOfWeek parameter to define the first day of the week.

FirstDayOfWeek	Description
1	Sunday (= Default value)
2	Monday
3	Tuesday
4	Wednesday
5	Thursday
6	Friday
7	Saturday

The optional FirstWeekOfYear parameter determines the first week of the year, which is defined by default as the week in which January 1 is located. The following definitions are possible here:

FirstWeekOfYear	Description
1	Week of January, 1st
2	Week in which at least four days of the new year are
3	first full week of the new year

Example:

Dim Diff As Long

Diff := DateDiff("d", DateSerial(2000, 5, 6), DateSerial(2000, 5, 7)) # retrieves 1

Diff := DateDiff("d", DateSerial(2000, 5, 7), DateSerial(2000, 5, 6)) # retrieves -1

Diff := DateDiff("ww", DateSerial(2000, 5, 7), DateSerial(2000, 6, 7)) # retrieves 5