Dim k As Date
Dim k2 As Date
Dim k3 As Date
Dim i As Long, j As Long
k = #9/17/2014 12:10:05 PM#
k2 = #1/1/1970#
i = DateDiff("s", k2, k)
j = i - 1800000
k3 = DateAdd("s", j, k)
'没指定开始日期,以做减法的日期为起点
MsgBox "从" & Format(k2, "yyyy-m-d h:m:s") & "到" & Format(k, "yyyy-m-d h:m:s") & "相差" & i & "秒" & vbCrLf & "从" & Format(k, "yyyy-m-d h:m:s") & "再过" & j & "秒是" & Format(k3, "yyyy-m-d h:m:s")
代码不做解释。条件也没说清。