Try using Access Help.
Returns a
Variant (
Long) specifying the number of time intervals between two specified dates.
Syntax
DateDiff(interval, date1, date2[
, firstdayofweek[
, firstweekofyear]]
)
The
DateDiff function syntax has these named arguments:
PartDescriptionintervalRequired.
String expression that is the interval of time you use to calculate the difference between
date1 and
date2.
date1,
date2Required;
Variant (
Date). Two dates you want to use in the calculation.
firstdayofweekOptional. A
constant that specifies the first day of the week. If not specified, Sunday is assumed.
firstweekofyearOptional. A constant that specifies the first week of the year. If not specified, the first week is assumed to be the week in which January 1 occurs.
Settings
The
interval argument has these settings:
SettingDescription
yyyy Year
q Quarter
m Month
y Day of year
d Day
w Weekday
ww Week
h Hour
n MinutesSecond
The
firstdayofweek argument has these settings:
ConstantValueDescriptionvbUseSystem0Use the NLS API setting.
vbSunday1Sunday (default)
vbMonday2Monday
vbTuesday3Tuesday
vbWednesday4Wednesday
vbThursday5Thursday
vbFriday6Friday
vbSaturday7Saturday
ConstantValueDescriptionvbUseSystem0Use the NLS API setting.
vbFirstJan11Start with week in which January 1 occurs (default).
vbFirstFourDays2Start with the first week that has at least four days in the new year.
vbFirstFullWeek3Start with first full week of the year.
Remarks
You can use the
DateDiff function to determine how many specified time intervals exist between two dates. For example, you might use
DateDiff to calculate the number of days between two dates, or the number of weeks between today and the end of the year.
To calculate the number of days between
date1 and
date2, you can use either Day of year ("y") or Day ("d"). When
interval is Weekday ("w"),
DateDiff returns the number of weeks between the two dates. If
date1 falls on a Monday,
DateDiff counts the number of Mondays until
date2. It counts
date2 but not
date1. If
interval is Week ("ww"), however, the
DateDiff function returns the number of calendar weeks between the two dates. It counts the number of Sundays between
date1 and
date2.
DateDiff counts
date2 if it falls on a Sunday; but it doesn't count
date1, even if it does fall on a Sunday.
If
date1 refers to a later point in time than
date2, the
DateDiff function returns a negative number.
The
firstdayofweek argument affects calculations that use the "w" and "ww" interval symbols.
If
date1 or
date2 is a date literal, the specified year becomes a permanent part of that date. However, if
date1 or
date2 is enclosed in double quotation marks (" "), and you omit the year, the current year is inserted in your code each time the
date1 or
date2 expression is evaluated. This makes it possible to write code that can be used in different years.
When comparing December 31 to January 1 of the immediately succeeding year,
DateDiff for Year ("yyyy") returns 1 even though only a day has elapsed.
Note For
date1 and
date2, if the
Calendar property setting is Gregorian, the supplied date must be Gregorian. If the calendar is Hijri, the supplied date must be Hijri.