ClosingTime example code for http://stackoverflow.com/q/27631882/97337

main.m

#import <Foundation/Foundation.h>
#import "WeekTimeRange.h"

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        NSArray *shopHours = @[WTMakeRange(Monday, 7, 30, Tuesday, 0, 0),
                               WTMakeRange(Tuesday, 7, 30, Wednesday, 0, 0),
                               WTMakeRange(Wednesday, 7, 30, Thursday, 0, 0),
                               WTMakeRange(Thursday, 7, 30, Friday, 0, 0),
                               WTMakeRange(Friday, 7, 30, Friday, 22, 0),
                               WTMakeRange(Saturday, 9, 0, Saturday, 22, 0),
                               WTMakeRange(Sunday, 9, 0, Monday, 2, 0)
                               ];

        WeekTime *mondayElevenPM = [[WeekTime alloc] initWithWeekday:Monday hour:23 minute:00];
        WeekTimeRange *openRange = WTFindOpenRangeIncluding(shopHours, mondayElevenPM);
        NSString *result = WTStatus(openRange, mondayElevenPM);
        NSLog(@"%@", result);
    }
    return 0;
}

WeekTime.h

#import <Foundation/Foundation.h>

typedef enum {
    Sunday,
    Monday,
    Tuesday,
    Wednesday,
    Thursday,
    Friday,
    Saturday
} Weekday;

/**
 A WeekTime is the first instant of a nominal minute within a week.
 Since it is nominal, it is not subject to DST adjustments. If a
 particular nominal minute occurs twice due to DST, then the WeekTime
 refers to the first instance of that minute. There are 7*24*60 nominal
 minutes in a nominal week.
 
 WeekTimes are subject to modular arithmetic (i.e. "they wrap around").
 This means that a WeekTime cannot be meaningfully compared to another
 WeekTime as greater-than or less-than. WeekTimes can be compared as
 equal or between a start and end.
 */
@interface WeekTime : NSObject

- (instancetype)initWithWeekday:(Weekday)weekday hour:(NSInteger)hour minute:(NSInteger)minute;

+ (NSInteger)maxMinute;

@property (nonatomic, readonly) NSInteger minutesSinceStartOfWeek;

@end

WeekTime.m

#import "WeekTime.h"

@implementation WeekTime

- (instancetype)initWithWeekday:(Weekday)weekday hour:(NSInteger)hour minute:(NSInteger)minute {
    NSParameterAssert(weekday >= Sunday && weekday <= Saturday);
    NSParameterAssert(hour >= 0 && hour < 24);
    NSParameterAssert(minute >= 0 && minute < 60);

    self = [super init];
    if (self != nil) {
        _minutesSinceStartOfWeek = weekday * 24 * 60 + hour * 60 + minute;
    }
    return self;
}

+ (NSInteger)maxMinute {
    return 7 * (24 * 60);
}

@end

WeekTimeRange.h

#import <Foundation/Foundation.h>
#import "WeekTime.h"

/**
 A range of WeekTimes, from the first instant of start to the first
 instant of end. Start is included, but end is not. Since WeekTimes
 are subject to modular arithmetic, end may be before start.
 start == end is currently undefined. You could choose to make it
 contain all times or no times. It depends on which is more useful.
 */
@interface WeekTimeRange : NSObject
@property (nonatomic, readonly) WeekTime *start;
@property (nonatomic, readonly) WeekTime *end;

- (instancetype)initWithStart:(WeekTime *)start end:(WeekTime *)end;
- (BOOL)contains:(WeekTime *)time;
@end

/** Convenience to make a WeekTimeRange */
WeekTimeRange *WTMakeRange(Weekday startDay, NSInteger startHour, NSInteger startMinute,
                           Weekday endDay, NSInteger endHour, NSInteger endMinute);

/** Return the first range in ranges that includes time. If no ranges
    include time, then nil. */
WeekTimeRange *WTFindOpenRangeIncluding(NSArray *ranges, WeekTime *time);

/** Figure out the Open/Closed/Closing string */
NSString *WTStatus(WeekTimeRange *range, WeekTime *requestedTime);

WeekTimeRange.m

#import "WeekTimeRange.h"

@implementation WeekTimeRange
- (instancetype)initWithStart:(WeekTime *)start end:(WeekTime *)end {
    NSInteger startMinutes = start.minutesSinceStartOfWeek;
    NSInteger endMinutes = end.minutesSinceStartOfWeek;
    NSParameterAssert(startMinutes != endMinutes);
    self = [super init];
    if (self != nil) {
        _start = start;
        _end = end;
    }
    return self;
}

- (BOOL)contains:(WeekTime *)time {
    NSInteger queryMinutes = time.minutesSinceStartOfWeek;
    NSInteger startMinutes = self.start.minutesSinceStartOfWeek;
    NSInteger endMinutes = self.end.minutesSinceStartOfWeek;

    if (startMinutes < endMinutes) {
        return (startMinutes <= queryMinutes &&
                queryMinutes < endMinutes);
    } else {
        return (queryMinutes < endMinutes ||
                queryMinutes >= startMinutes);
    }
}
@end

WeekTimeRange *WTMakeRange(Weekday startDay, NSInteger startHour, NSInteger startMinute,
                           Weekday endDay, NSInteger endHour, NSInteger endMinute) {
    return [[WeekTimeRange alloc]
            initWithStart:[[WeekTime alloc] initWithWeekday:startDay hour:startHour minute:startMinute]
            end:[[WeekTime alloc] initWithWeekday:endDay hour:endHour minute:endMinute]];
}

WeekTimeRange *WTFindOpenRangeIncluding(NSArray *ranges, WeekTime *time) {
    for (WeekTimeRange *range in ranges) {
        if ([range contains:time]) {
            return range;
        }
    }
    return nil;
}

NSString *WTStatus(WeekTimeRange *range, WeekTime *requestedTime) {
    if (range != nil) {
        NSInteger minutesLeft = range.end.minutesSinceStartOfWeek - requestedTime.minutesSinceStartOfWeek;
        if (minutesLeft < 0) {
            minutesLeft += [WeekTime maxMinute];
        }
        if (minutesLeft <= 30) {
            return [NSString stringWithFormat:@"Closing in %ld minutes", (long)minutesLeft];
        } else {
            return @"Open";
        }
    } else {
        return @"Closed";
    }
}