Yaakov: one thing i can tell, if you are dealing with a NY purchase, under NY General Construction Law § 20, the day of the purchase is not included in the computation:
“The proper method when computing time periods is to exclude the day of the event and to include the last day up to midnight of that day.” Bacalokonstantis v. Nichols, 141 A.D.2d 482, 484, 529 N.Y.S.2d 111, 113 (2d Dept. 1988) (citing New York General Construction Law § 20); accord, e.g., Austrian Lance & Stewart, P.C. v. Rockefeller Ctr., Inc., 163 A.D.2d 125, 130, 558 N.Y.S.2d 521, 525 (1st Dep’t 1990) (where period for tenant to cure default was “denoted in days rather than hours,” period ran until midnight on the last day designated for the cure) (citing New York General Construction Law § 20); Antine v. City of New York, 14 Misc. 3d 161, 172-73, 830 N.Y.S.2d 430, 439 (Sup. Ct. N.Y. Co. 2006); Alvarez v. Warden, 178 Misc. 2d 254, 255, 680 N.Y.S.2d 153, 154 (Sup. Ct. Bronx Co. 1998) Union Mutual Life Ins. Co. v. Kevie, 17 A.D.2d 109, 110, 232 N.Y.S.2d 678, 679 (1st Dep’t 1962), aff’d, 13 N.Y.2d 971, 194 N.E.2d 686, 244 N.Y.S.2d 777 (1963).
So if you had, lets say, 10 days to return, you get 10 days starting the day after the purchase. Other states have similar laws.