Illegal or not? Withholding of security deposit

[polypam]

In July, I moved out of my shared apartment in Manhattan to move to my own pad in Brooklyn. I found the place very quickly and was unable to give my roommate a full 4 weeks notice, though I did give him three. It took a month and half and a threatening letter to get my deposit back from him. However, he withheld 8 days of rent because I didn't give him 4 weeks notice. Is this legal? He is the only one on the lease. I never signed anything with him saying that I had to give 4 weeks notice if I moved out and I don't think it's an actual law that you need to (though I could be wrong). Any answers would be greatly appreciated. Also, I remember there is some hotline number that you can call to ask these sort of questions but I cannot find it. Anyone know it??? THANKS!

[consigliere]

In New York City, a landlord -- but not a tenant -- has to give 30 days' notice to terminate a month-to-month tenancy.
 
Real Property Law §232-a provides:
 
Notice to terminate monthly tenancy or tenancy from month to month in the city of New York
 
No monthly tenant, or tenant from month to month, shall hereafter be removed from any lands or buildings in the city of New York on the grounds of holding over his term unless at least thirty days before the expiration of the term the landlord or his agent serve upon the tenant, in the same manner in which a notice of petition in summary proceedings is now allowed to be served by law, a notice in writing to the effect that the landlord elects to terminate the tenancy and that unless the tenant removes from such premises on the day on which his term expires the landlord will commence summary proceedings under the statute to remove such tenant therefrom.