The DateDiff, DateAdd and DatePart VBScript Functions

The Datediff function

The Datediff function is a great way to calculate the interval period between two dates. If you set the interval parameter to m for months the function will return the amount of months between the two dates. The table below lists the interval periods you can set for the interval parameter.

Syntax: DateDiff(Interval,date1,date2)

Interval	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

<%
Response.write DateDiff("m","01/01/04",date) & " Months"
'date function returns todays date so its difference between 01/01/04 & today
%>

Output: 52 Months

The DateAdd function

The DateAdd() functions allows us to add or subtract from a date or time. DateAdd returns a date or time that has been modified by the number parameter.

Syntax: DateAdd(Interval, number, Date)

The interval argument accepts the following values:

Interval	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

<%
Response.write DateAdd("m",2,date)
'the date function returns today's date so we are adding 2 months on
'you can also substract i.e. -2
%>

Output: 12/07/2008
'this is UK format as the server is in the UK

<%
Response.write DateAdd("n",-25,time)
'the time function returns today's time so we are substracting 25 minutes
%>

Output: 04:32:14

The DatePart function

We can use the DatePart function to return the specified part of the date and time.

Syntax: DatePart(GetPartOftheDate, Date)

The GetPartoftheDate argument accepts the following values:

GetPartoftheDate	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

<%
Response.write "The Now function returns:" & Now & "<br>"
Response.write "Retrieve the year: " & DatePart("yyyy", Now)
%>

OutPut: The Now function returns:12/05/2008 04:57:14
Retrieve the year: 2008

Other date and time related tutorials:
Here's a code snippet to display the day and date (eg. Mon 25 December).
Here's a code snippet to display the day and date with the ordinal suffix (eg. Mon 25th December).
How to get the current month name
Display the dates and times
Time and Date based greetings
IsDate Function

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