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DateDiff - function of language VBScript

Description:
Returns the number of intervals between two dates.

For the purposes of PROMOTIC system, it is more usefull to use the method: Pm.DateDiff.

Syntax:
DateDiff(interval As String, date1 As Date, date2 As Date, [firstdayofweek As Integer], [firstweekofyear As Integer]) As Long
Calling:
n = DateDiff(interval, date1, date2[, firstdayofweek[, firstweekofyear]])
Parameters:
interval(String) Specifies the interval (type of time range) used to calculate the difference between date1 and date2
"yyyy" - year
"q" - quarter
"m" - month
"y" - day of year
"d" - day
"w" - day of the week
"ww" - week of year
"h" - hour
"n" - minute
"s" - second
date1(Date) First date in the calculation
date2(Date) Second date in the calculation
firstdayofweek[optional] (Integer) Specifies the first day of the week.

If not set, then Sunday is assumed (see VBScript Date and Time constants).

This argument affects calculations that use the "w" and "ww" interval symbols.

firstweekofyear[optional] (Integer) Specifies the first week of year.

If not set, then the first week is assumed to be the week in which 1st January occurs (see VBScript Date and Time constants).

Note:

To calculate the number of days between date1 and date2, can be used day of year ("y") or day ("d").

 
If interval is day of the week ("w"), then function returns the number of weeks between the two dates. If date1 falls on a Monday, then function counts the number of of Mondays until date2. It counts date2 but not date1. If interval is week ("ww"), however, then function returns the number of calendar weeks between the two dates. Function counts the number of Sundays between date1 and date2. Function counts date2 if it falls on a Sunday; but it doesn't count date1, even if it does fall on a Sunday.
 
If is date1 > date2, then the function returns a negative number.
 
If date1 or date2 is a date literal, then the specified year becomes a permanent part of that date. However, if date1 or date2 is enclosed in quotation marks (" ") and you omit the year, then the current year is inserted in your code each time the date1 or date2 expression is evaluated. This makes it possible to write script that can be used in different years.
 
When comparing December 31 to January 1 of the immediately succeeding year, function for year ("yyyy") returns 1 even if only a day has elapsed.
Example:
Detects the number of days between a given date tDate and today
VBScriptSelect and copy to clipboard

Dim s
s = "The number of days from today: " & DateDiff("d", Now(), tDate)
PROMOTIC 9.0.0 SCADA system documentation - MICROSYS, spol. s r.o.

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