FUNCTION:  DateDiff( )
Implemented in version 2.0
 
DateDiff(Interval, Date1, Date2, FirstDayofWeek, FirstWeekofYear)
 
The DateDiff function calculates the amount of time between two different dates.
 
There are three mandatory arguments.
 
Interval
 
The Interval argument defines the the type of time interval you wish to use to calculate the time difference.
 
Only the following settings can be used. You must place the setting inside a pair of double quotes.
 
SETTING DESCRIPTION
YYYY Year
Q Quarter
M Month
Y Day Of Year
D Day
W WeekDay
WW Week Of Year
H Hour
N Minute
S Second

 
Date1
 
The Date1 argument is the first date.
 
Date2
 
The Date2 argument is the second date.
 
Code:
<%=DateDiff("d", Date, "1/1/2000") %>
 
Output:
291
 
The order of the two dates determines if the difference is represented as a positive or negative value.
 
Code:
<% olddate = #6/26/43# %>
<% nowdate = Now %>
<% =DateDiff("s", nowdate, olddate) %>
 
Output:
-3130748108
 
There are two optional arguments.
 
FirstDayofWeek
 
The FirstDayofWeek argument must only use the constants or values defined below in the Date And Time CONSTANTS.
 
CONSTANT VALUE DESCRIPTION
VBSunday 1 Sunday
VBMonday 2 Monday
VBTuesday 3 Tuesday
VBWednesday 4 Wednesday
VBThursday 5 Thursday
VBFriday 6 Friday
VBSaturday 7 Saturday
VBFirstJan1 1 Week of January 1
VBFirstFourDays 2 First week of the year that has at least four days
VBFirstFullWeek 3 First full week of the year
VBUseSystem 0 Use the date format of the computer's regionsl settings
VBUseSystemDayOfWeek 0 Use the first full day of the week as defined by the system settings

 
In this example, Tuesday is defined to be the first day of the week. The output is how many weeks, which are now defined to start on Tuesday, are left between the current date and 1/1/2001.
 
Code:
<% =DateDiff("w", Date, "1/1/2001", 3) %>
 
Output:
93
 
Code:
<% =DateDiff("w", Date, "1/1/2001", VBTUESDAY) %>
 
Output:
93
 
FirstWeekofYear
 
The FirstWeekofYear argument must only use the constants or values defined in the Date And Time CONSTANTS which are listed above.
 
Code:
<% =DateDiff("ww", Date, "1/1/2001", 1, VBFIRSTFOURDAYS)%>
 
Output:
94