[ios]字符串转化成NSDate类型 计算与当前时间的相差 月数 天数 【转】

NSString *dateStr=[dic objectForKey:@"date"];// 2012-05-17 11:23:23

NSCalendar *gregorian = [[NSCalendaralloc] initWithCalendarIdentifier:NSGregorianCalendar];

NSUInteger unitFlags = NSMonthCalendarUnit | NSDayCalendarUnit;

NSDateFormatter *format=[[NSDateFormatteralloc] init];

[format setDateFormat:@"yyyy-MM-dd HH:mm:ss"];

NSDate *fromdate=[format dateFromString:dateStr];

NSTimeZone *fromzone = [NSTimeZone systemTimeZone];

NSInteger frominterval = [fromzone secondsFromGMTForDate: fromdate];

NSDate *fromDate = [fromdate dateByAddingTimeInterval: frominterval];

NSLog(@"fromdate=%@",fromDate);

[format release];

NSDate *date = [NSDate date];

NSTimeZone *zone = [NSTimeZonesystemTimeZone];

NSInteger interval = [zone secondsFromGMTForDate: date];

NSDate *localeDate = [date dateByAddingTimeInterval: interval];

NSLog(@"enddate=%@",localeDate);

NSDateComponents *components = [gregorian components:unitFlags fromDate:fromDate toDate:localeDate options:0];

NSInteger months = [components month];

NSInteger days = [components day];//年[components year]

NSLog(@"month=%d",months);

NSLog(@"days=%d",days);

[gregorian release];

if (months==0&&days==0) {

dateStr=[[dateStr substringFromIndex:11]substringToIndex:5];

cell.textLabel.text=[NSString stringWithFormat:@"今天 %@",dateStr];//今天 11:23

}else if(months==0&&days==1){

dateStr=[[dateStr substringFromIndex:11]substringToIndex:5];

cell.textLabel.text=[NSString stringWithFormat:@"昨天 %@",dateStr];//昨天 11:23

}else{

dateStr=[dateStr substringToIndex:10];

cell.textLabel.text=dateStr;

}