日期相减的问题
Mysqlcommand.Commandtext="SELECT TOP 1 time from content Where customerid='" & id & "' ORDER BY id DESC"
MysqlRead=Mysqlcommand.Executereader
If MysqlRead.Read Then
ontime=MysqlRead.item("time")
End If
ttime=now
stringtime=Convert.ToInt32(ttime)- Convert.ToInt32(ontime)
If stringtime>1 Then
Response.Write("<script language=javascript for=window event=onload>window.alert('您已经" + stringtime + "没有联系此客户了!')</" & "script>")
End If
请问怎么样才能让字符串的日期相减?