It’s been a month since Forsyth County and the city of Cumming began allowing stores to sell alcohol on Sundays.But representatives at most beverage stores say they need more time before they can determine the full impact the change may have on their bottom line. “With St. Patty’s Day, Easter and spring break, it’s been too soon to tell,” said Nathan Popky, president of Pop’s Wine & Spirits on Peachtree Parkway in south Forsyth.He noted that all of those events led to higher than normal sales, adding that they’ll “probably need a full year to really tell the difference” with Sundays.On March 6, voters in both local jurisdictions overwhelming approved Sunday sales, with margins of 69 and 61 percent, respectively. Nearly 99.6 percent of the 31,505 voters who cast ballots weighed in on the issue.