Script needed

Hi
I am looking for the script which can move 1month old data from a TXT file.actully in this file data is appended on daily basis.pleasehalp me out.

Thanks in advance

Please give an example of your data file and what you want to obtain.

Here is the file content :
$head abc.txt
20070301130052,xxz
20070307132111,cvasjchgjhcg
gacg
chjbgasjkchjk
20070307133029,gcvashcvgjchklk
20070308070017,hbcjkbgcjkhk
20070308084700,hjcgjhcg
20070308114137,kjcghjk

$tail abc.txt
20080304113050,cgsjkchskjchskch
20080304113053,cvbnsckhhkhcjs
cjksdhcklsjcl
20080304120046,cvbsdcbksdhj
cvhbskcvnhsdkl
svjscvkmj
20080304120048,vgsdjkv
vbsdkvhj
vnsdvlmj
vnm

I want to remain only one month data in this file and cut other data and mv that into new location.