Convert a multiple year list of 365 days/year into an equivalent of 360 days/year

Good Evening everyone in the forum
this is my first post.
I am a debutant with climate modelling and I want to do daily analysis (temperatures, rains) ..so my software produce a 10 year column (365values*10 + leap years)
Unfortunately some english climate models produce series of 360 days/year that the software is not able to recognize and print via excel (I have 2003 version) 365days year.
This is a problem because enlarging the serie to decades the 5 days gap get bigger and completaly flip flop season producing outputs labeled as december that are actually in august...

My question is if having a single column daily values in 365 or 366 days a year

01/01/1951
02/01/1951
. . .
31/01/1951
01/02/1951
. . .
. . .
. . .
28/02/1951
01/03/1951

can be converted (with a macro???) in a 30 day a month (and 360 days a yeear list

01/01/1951
02/01/1951
. . .
30/01/1951
01/02/1951
. . .
. . .
. . .
30/02/1951
01/03/1951
.
.
.
.
.
30/12/2099


I hope it was clear

Thanks for any help you can provide

Cheers

Andrea

? First day 1/1/1900 (365) <=> 1/1/1900 (360)

#1/1/1900# <> @1/1/1900@
#7/23/2012# => @DD/MM/yyyy@

NumDate = CLng(DateSerial(2012, 7, 23))

yyyy = 1900 + Int(NumDate / 360)

MM = Int((NumDate mod 360) / 30)

DD = NumDate - yyyy * 360 - MM * 30

=> @2/13/2014@

ehy thank youvery much for answering so quickly!

I have a problem on your answer
is "dateserial" a function in excel? because i am afraid excel does not recognize it (2003 or 2010).
what actually the @ symbols means?
Thanks
cheers
andrea

DataSerial(Year,Month,Day): this is Function in VBA

(In VBA)
#2/13/2012# Date type for normal;

@2/13/2014@ Date type for You!

Many thanks for your reply again
I got the logic of the commands

yyyy = 1900 + Int(NumDate / 360)
MM = Int((NumDate mod 360) / 30)
DD = NumDate - yyyy * 360 - MM * 30

and i implemented them in a macro

But still I dont get the meaning of these 2 strings (the begin and the end of the series )
#1/1/1900# <> @1/1/1900@
#7/23/2012# => @DD/MM/yyyy@

why the sign <> (it means differs right?) and should i type 1/1/1900 or should I type the cell (line, column) where is located?

many thanks