尝试使用其他变量设置日期和时间。“时间”内置于VBA中，将返回当前时间和范围（“I15”）。值将设置为当前时间，而不是所需的08：00

Dim wksdata As Worksheet
Dim xyz as String
Dim startTime as String

Set wksdata = Sheets("Data")
startTime = Date + TimeValue("08:00:00") 'Set Time value as todays date 8am
Worksheets("Calculations").Range("I15").Value = startTime 'set calculations 
worksheet cell I15 as the time value

Worksheets("Data)").Range("U:U").NumberFormat = "dd/mm/yyyy hh:mm:ss"  
'converts time column to time format

xyz = WorksheetFunction.CountIfs(wksdata.Range("I:I"), "xyz", 
wksdata.Range("K:K"), "C", wksdata.Range("U:U"), "<" & 
Worksheets("Calculations").Range("I15").Value)

需要将日期部分转换为长整型。完成此操作后，公式将正常工作。以下是使用类似公式完成此操作的示例：

Sub test_method()

Range("B1") = Now()
Range("B1").NumberFormat = "dd/mm/yyyy hh:mm:ss"

'Trying to calculate using a VBA date in the worksheet formula doesn't work
'This returns 0
Debug.Print WorksheetFunction.CountIfs(Range("B1:B10"), ">" & (Now() - 0.75))

'Now we change it to a long and it yields the correct answer
'returns 1
Debug.Print WorksheetFunction.CountIfs(Range("B1:B10"), ">" & CLng((Now() - 0.75)))

End Sub