Address Book does not show changes to Birthday

I transferred all my contacts to my Mac, and while synching with iPod was warned of differences in birthdays.

I wrote a script to extract all birthdays to a file and found they were all off by 1 day.
No problem, I will just write a script (below) to increment them.

This seemed to work, and the dates extracted by my script seemed to have been fixed.

Unfortunately looking in Address Book did not reflect the changes.
Logging off an on did not make any difference, although the dates extracted by my script had reverted to the original.

Can anyone explain this, and tell me how to make the changes permanent.

# Increment all Birth Dates by 1 day
tell application "Address Book"
	set birthPeople to (people whose birth date is not missing value)
	repeat with n from 1 to (count of birthPeople)
		set cBirth to (birth date of (item n of birthPeople))
		set nBirth to cBirth + 24 * 60 * 60
		set (birth date of (item n of birthPeople)) to nBirth
	end repeat
end tell

Model: MacBook Pro
Browser: Safari 533.21.1
Operating System: Mac OS X (10.6)


in Snow Leopard you have to save the address book explicitly

	end repeat
end tell