使用列表排序方法：

In [1]: from datetime import date, timedelta

In [2]: a=[date.today(), date.today() + timedelta(days=1), date.today() - timedelta(days=1)]

In [3]: a
Out[3]: 
[datetime.date(2012, 3, 28),
 datetime.date(2012, 3, 29),
 datetime.date(2012, 3, 27)]

In [4]: a.sort()

In [5]: a
Out[5]: 
[datetime.date(2012, 3, 27),
 datetime.date(2012, 3, 28),
 datetime.date(2012, 3, 29)]

In [6]: a[0] # min
Out[6]: datetime.date(2012, 3, 27)

In [7]: a[-1] # max
Out[7]: datetime.date(2012, 3, 29)

有关如何排序的更多信息。