NSString *dateString=@"2015-09-30";
NSDateFormatter *dateFormatter=[[NSDateFormatter alloc]init];
[dateFormatter setDateFormat:@"yyyy-MM-dd"];
myData = [dateFormatter dateFromString:dateString];
NSString2015-09-30转化为NSData
原文：http://www.cnblogs.com/zhanghuifeng/p/4789991.html
