在 Microsoft Access (2010) 中以年和月为单位计算年龄

Question

我有两个字段（体检日期和出生日期）。我计算了年龄（（体检日期-出生日期）/365.25）。我想做的是在单独的字段中以年和月为单位计算年龄。我不确定是否可以使用代码生成器或其他方式来完成。

Answer 1

处理更精细的细节需要多一点（就像一年计算一样）：

Public Function Months( _
  ByVal datDate1 As Date, _
  ByVal datDate2 As Date, _
  Optional ByVal booLinear As Boolean) _
  As Integer

' Returns the difference in full months between datDate1 and datDate2.
'
' Calculates correctly for:
'   negative differences
'   leap years
'   dates of 29. February
'   date/time values with embedded time values
'   negative date/time values (prior to 1899-12-29)
'
' Optionally returns negative counts rounded down to provide a
' linear sequence of month counts.
' For a given datDate1, if datDate2 is decreased stepwise one month from
' returning a positive count to returning a negative count, one or two
' occurrences of count zero will be returned.
' If booLinear is False, the sequence will be:
'   3, 2, 1, 0,  0, -1, -2
' If booLinear is True, the sequence will be:
'   3, 2, 1, 0, -1, -2, -3
'
' If booLinear is False, reversing datDate1 and datDate2 will return
' results of same absolute Value, only the sign will change.
' This behaviour mimics that of Fix().
' If booLinear is True, reversing datDate1 and datDate2 will return
' results where the negative count is offset by -1.
' This behaviour mimics that of Int().

' DateAdd() is used for check for month end of February as it correctly
' returns Feb. 28. when adding a count of months to dates of Feb. 29.
' when the resulting year is a common year.
'
' 2010-03-30. Cactus Data ApS, CPH.

  Dim intDiff   As Integer
  Dim intSign   As Integer
  Dim intMonths As Integer

  ' Find difference in calendar months.
  intMonths = DateDiff("m", datDate1, datDate2)
  ' For positive resp. negative intervals, check if the second date
  ' falls before, on, or after the crossing date for a 1 month period
  ' while at the same time correcting for February 29. of leap years.
  If DateDiff("d", datDate1, datDate2) > 0 Then
    intSign = Sgn(DateDiff("d", DateAdd("m", intMonths, datDate1), datDate2))
    intDiff = Abs(intSign < 0)
  Else
    intSign = Sgn(DateDiff("d", DateAdd("m", -intMonths, datDate2), datDate1))
    If intSign <> 0 Then
      ' Offset negative count of months to continuous sequence if requested.
      intDiff = Abs(booLinear)
    End If
    intDiff = intDiff - Abs(intSign < 0)
  End If

  ' Return count of months as count of full 1 month periods.
  Months = intMonths - intDiff

End Function

Answer 2

虽然DateDiff() 函数似乎是计算年龄的合乎逻辑的选择，但不幸的是，它不能计算两个日期之间经过的完整年或月数。例如，假设一个婴儿于 2014 年 12 月 31 日出生，并在 48 小时后的 2015 年 1 月 2 日进行了检查。也就是说，

DateOfBirth = DateSerial(2014, 12, 31)
DateOfExam = DateSerial(2015, 1, 2)

如果我们简单地使用DateDiff() 来计算她在考试时的“年龄”，以年和月为单位，我们会得到

?DateDiff("yyyy", DateOfBirth, DateOfExam)
 1 
?DateDiff("m", DateOfBirth, DateOfExam)
 1 

因此，我们会报告婴儿 1 岁零 1 个月大，而实际上她只有 2 天 大。

正确的年龄计算需要比这更复杂。以下 VBA 函数将以年和月为单位计算“年龄”，返回类似“2 年零 1 个月”的字符串：

Public Function AgeInYearsAndMonths(StartDate As Variant, EndDate As Variant) As Variant
    Dim Date1 As Date, Date2 As Date
    Dim mm1 As Integer, dd1 As Integer, mm2 As Integer, dd2 As Integer
    Dim ageYears As Integer, ageMonths As Integer, rtn As Variant
    rtn = Null
    If Not (IsNull(StartDate) Or IsNull(EndDate)) Then
        If StartDate <= EndDate Then
            Date1 = StartDate
            Date2 = EndDate
        Else
            Date1 = EndDate
            Date2 = StartDate
        End If
        mm1 = Month(Date1)
        dd1 = Day(Date1)
        mm2 = Month(Date2)
        dd2 = Day(Date2)
        ageYears = DateDiff("yyyy", Date1, Date2)
        If (mm1 > mm2) Or (mm1 = mm2 And dd1 > dd2) Then
            ageYears = ageYears - 1
        End If
        ageMonths = DateDiff("m", Date1, Date2) Mod 12
        If dd1 > dd2 Then
            If ageMonths = 0 Then
                ageMonths = 12
            End If
            ageMonths = ageMonths - 1
        End If
        If ageYears = 0 And ageMonths = 0 Then
            rtn = "less than 1 month"
        Else
            rtn = ageYears & " year" & IIf(ageYears = 1, "", "s") & " and " & ageMonths & " month" & IIf(ageMonths = 1, "", "s")
        End If
    End If
    AgeInYearsAndMonths = rtn
End Function