Exclude date from sumif

Hi there,
I have a situation where i need to exclude from a column, a cell with a date and sumif the rest of the numbers. I do know that excel treats date as numbers. How do i write the sumif statement in this case?
Example.

1
10
1
10
12/31/2012
1
10
1
10

Generous help is appreciated...

The value of 01/01/2012 is 40909, 02/01/2012 is 40910 and so on,

if you know that your values will be smaller than that, what I would do is simply =sumif(range,"<40910")

Otherwise a simple vba code can do what you want. Without vba, I wouldn't know, sorry.

Thank you everyone.
Sumif did provide a better performance compared to sumproduct but the weird thing is that sumproduct did not calculate anything and gave me a 0 value.
Sumif works perfectly.