VB：1给定一个四位数的年份，判断它是否为闰年。

Private Sub Command1_Click()
x = InputBox("输入年份")
If IsLeapYearB(x) = True Then
Print x & "是闰年"
Else
Print x & "不是"
End If
a = InputBox("输入年份")
b = InputBox("输入月份")
Print LastDay(a, b) & "天"
End Sub
Public Function IsLeapYearB(ByVal yr As Integer) As Boolean
IsLeapYearB = Day(DateSerial(yr, 2, 29)) = 29
End Function

Public Function LastDay(ByVal testYear As Integer, ByVal testMonth As Integer) As Integer
LastDay = Day(DateSerial(testYear, testMonth + 1, 0))
End Function

'这两个问题实际可以归结为一个问题，即求某年某月有多少天，调用下面仅 1 条语句的简单函数就可以实现：
'窗体添加控件 Command1、Command2 就可以查看 GetDays 的用法
Private Function GetDays(nYear As Long, nMonth As Long) As Long
GetDays = Day(DateSerial(nYear, nMonth + 1, 0))
End Function

'问题1，通过判断 2 月份是否有 29 天确定是否闰年
Private Sub Command1_Click()
Dim nYear As Long
nYear = Val(