Detecting dates using SUMIF....

i'm creating a spreadsheet which calculates my incomes and outgoings for the year. In column D I am entering the date as (eg) '7 Jan' yet when I try the formula below I'm still unable to detect which month has been entered..

=SUMIF(D9:D40,"jan",C9:C40)

I know it would be possible to correct this if I create a separate column just for the month but surely it must be possible to detect the word 'jan' by ignoring the numbers and spaces..
I'd appreciate any help.

If your entries in column D are text then this should work

=SUMIF(D9:D40,"*jan*",C9:C40)

Note the wildcards

but if the entries are interpreted as true dates try

=SUMPRODUCT((TEXT(D9:D40,"mmm")="Jan")*(D9:D40<>""),C9:C40)

Thanks very much. Works a treat