Provided by Allen Browne.
Given a person's date-of-birth, how do you calculate their age? These examples do not work reliably:
Format(Date() - DOB, "yyyy") DateDiff("y", DOB, Date) Int(DateDiff("d", DOB, Date)/365.25)
DateDiff("y", ..., ...) merely subtracts the year parts of the dates, without reference to the month or day. This means we need to subtract one if the person has not has their birthday this year. The following expression returns True if the person has not had their birthday this year:
DateSerial(Year(Date), Month(DOB), Day(DOB)) > Date
True equates to -1, so by adding this expression, Access subtracts one if the birthday hasn't occurred.
The function is therefore:
Function Age(varDOB As Variant, Optional varAsOf As Variant) As Variant 'Purpose: Return the Age in years. 'Arguments: varDOB = Date Of Birth ' varAsOf = the date to calculate the age at, or today if missing. 'Return: Whole number of years. Dim dtDOB As Date Dim dtAsOf As Date Dim dtBDay As Date 'Birthday in the year of calculation. Age = Null 'Initialize to Null 'Validate parameters If IsDate(varDOB) Then dtDOB = varDOB If Not IsDate(varAsOf) Then 'Date to calculate age from. dtAsOf = Date Else dtAsOf = varAsOf End If If dtAsOf >= dtDOB Then 'Calculate only if it's after person was born. dtBDay = DateSerial(Year(dtAsOf), Month(dtDOB), Day(dtDOB)) Age = DateDiff("yyyy", dtDOB, dtAsOf) + (dtBDay > dtAsOf) End If End If End Function
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