解决方法
xlrd不将日期转换为float. Excel将日期存储为浮点数.
报价从the xlrd documentation(向下滚动一页)：
Dates in Excel spreadsheets
In reality,there are no such things.
What you have are floating point
numbers and pIoUs hope. There are
several problems with Excel dates:(1) Dates are not stored as a separate
data type; they are stored as floating
point numbers and you have to rely on
(a) the “number format” applied to
them in Excel and/or (b) knowing which
cells are supposed to have dates in
them. This module helps with (a) by
inspecting the format that has been
applied to each number cell; if it
appears to be a date format,the cell
is classified as a date rather than a
number.
另请参阅Cell类的部分,以及提取单元格类型(文本,数字,日期,布尔等)的各种Sheet方法.
还可以阅读可从www.python-excel.org访问的教程