macOS Date Time Objective-C Samples

// macOS Objective-C NSDate Basics
// Using Foundation framework

#import <Foundation/Foundation.h>

// MARK: - 1. Creating Dates

@interface DateCreation : NSObject

+ (void)demonstrateCreation {
    NSLog(@"--- Date Creation ---");

    // Current date
    NSDate *now = [NSDate date];
    NSLog(@"Current date: %@", now);

    // Distant past
    NSDate *past = [NSDate distantPast];
    NSLog(@"Distant past: %@", past);

    // Distant future
    NSDate *future = [NSDate distantFuture];
    NSLog(@"Distant future: %@", future);

    // Tomorrow
    NSDate *tomorrow = [NSDate dateWithTimeIntervalSinceNow:86400];
    NSLog(@"Tomorrow: %@", tomorrow);

    // Yesterday
    NSDate *yesterday = [NSDate dateWithTimeIntervalSinceNow:-86400];
    NSLog(@"Yesterday: %@", yesterday);

    // Specific date
    NSDateComponents *components = [[NSDateComponents alloc] init];
    components.year = 2024;
    components.month = 12;
    components.day = 25;

    NSCalendar *calendar = [NSCalendar currentCalendar];
    NSDate *christmas = [calendar dateFromComponents:components];
    NSLog(@"Christmas 2024: %@", christmas);

    // From string
    NSString *dateString = @"2024-12-25 14:30:00";
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    formatter.dateFormat = @"yyyy-MM-dd HH:mm:ss";

    NSDate *parsed = [formatter dateFromString:dateString];
    NSLog(@"Parsed date: %@", parsed);

    // Unix timestamp
    NSDate *fromTimestamp = [NSDate dateWithTimeIntervalSince1970:1703500000];
    NSLog(@"From timestamp: %@", fromTimestamp);
}

@end

// MARK: - 2. Date Comparison

@interface DateComparison : NSObject

+ (void)demonstrateComparison {
    NSLog(@"\n--- Date Comparison ---");

    NSDate *now = [NSDate date];
    NSDate *past = [NSDate dateWithTimeIntervalSinceNow:-3600];
    NSDate *future = [NSDate dateWithTimeIntervalSinceNow:3600];

    // Compare
    NSComparisonResult result = [now compare:past];

    if (result == NSOrderedAscending) {
        NSLog(@"Now < Past");
    } else if (result == NSOrderedDescending) {
        NSLog(@"Now > Past");
    } else {
        NSLog(@"Now == Past");
    }

    // Earlier/Later
    BOOL isEarlier = ([past compare:now] == NSOrderedAscending);
    BOOL isLater = ([future compare:now] == NSOrderedDescending);

    NSLog(@"Past is earlier than now: %@", isEarlier ? @"YES" : @"NO");
    NSLog(@"Future is later than now: %@", isLater ? @"YES" : @"NO");

    // Between dates
    NSDate *start = [NSDate dateWithTimeIntervalSinceNow:-7200];
    NSDate *end = [NSDate dateWithTimeIntervalSinceNow:7200];

    BOOL isBetween = ([now compare:start] == NSOrderedDescending) &&
                    ([now compare:end] == NSOrderedAscending);

    NSLog(@"Now is between start and end: %@", isBetween ? @"YES" : @"NO");

    // Equal dates (within tolerance)
    NSDate *date1 = [NSDate date];
    [NSThread sleepForTimeInterval:0.1];
    NSDate *date2 = [NSDate date];

    NSTimeInterval tolerance = 1.0; // 1 second
    BOOL isEqual = fabs([date1 timeIntervalSinceDate:date2]) < tolerance;

    NSLog(@"Dates equal (within %.0fs): %@", tolerance, isEqual ? @"YES" : @"NO");
}

@end

// MARK: - 3. Date Intervals

@interface DateIntervals : NSObject

+ (void)demonstrateIntervals {
    NSLog(@"\n--- Date Intervals ---");

    NSDate *start = [NSDate date];

    // Time interval since date
    NSTimeInterval interval = [start timeIntervalSinceNow];
    NSLog(@"Interval since now: %.0f seconds", interval);

    // Add time interval
    NSDate *plusOneHour = [start dateByAddingTimeInterval:3600];
    NSLog(@"Plus one hour: %@", plusOneHour);

    // Days from now
    NSDate *sevenDaysLater = [NSDate dateWithTimeIntervalSinceNow:7 * 86400];
    NSLog(@"Seven days later: %@", sevenDaysLater);

    // Days ago
    NSDate *thirtyDaysAgo = [NSDate dateWithTimeIntervalSinceNow:-30 * 86400];
    NSLog(@"Thirty days ago: %@", thirtyDaysAgo);

    // Time between dates
    NSDate *date1 = [NSDate dateWithTimeIntervalSince1970:0];
    NSDate *date2 = [NSDate date];

    NSTimeInterval secondsBetween = [date2 timeIntervalSinceDate:date1];
    NSLog(@"Seconds between dates: %.0f", secondsBetween);

    NSInteger daysBetween = floor(secondsBetween / 86400);
    NSLog(@"Days between: %ld days", (long)daysBetween);

    // Calculate age
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    formatter.dateFormat = @"yyyy-MM-dd";

    NSDate *birthDate = [formatter dateFromString:@"1990-06-15"];
    NSTimeInterval ageInSeconds = [[NSDate date] timeIntervalSinceDate:birthDate];

    NSInteger ageInYears = floor(ageInSeconds / (365.25 * 24 * 3600));
    NSLog(@"Age: %ld years", (long)ageInYears);
}

@end

// MARK: - 4. NSDateFormatter

@interface DateFormatting : NSObject

+ (void)demonstrateFormatting {
    NSLog(@"\n--- Date Formatting ---");

    NSDate *now = [NSDate date];

    // Predefined styles
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];

    formatter.dateStyle = NSDateFormatterShortStyle;
    formatter.timeStyle = NSDateFormatterNoStyle;
    NSLog(@"Short date: %@", [formatter stringFromDate:now]);

    formatter.dateStyle = NSDateFormatterMediumStyle;
    formatter.timeStyle = NSDateFormatterShortStyle;
    NSLog(@"Medium date, short time: %@", [formatter stringFromDate:now]);

    formatter.dateStyle = NSDateFormatterLongStyle;
    formatter.timeStyle = NSDateFormatterLongStyle;
    NSLog(@"Long date, long time: %@", [formatter stringFromDate:now]);

    formatter.dateStyle = NSDateFormatterFullStyle;
    formatter.timeStyle = NSDateFormatterFullStyle;
    NSLog(@"Full style: %@", [formatter stringFromDate:now]);

    // Custom formats
    formatter.dateFormat = @"yyyy-MM-dd";
    NSLog(@"ISO date: %@", [formatter stringFromDate:now]);

    formatter.dateFormat = @"MMMM dd, yyyy";
    NSLog(@"Readable: %@", [formatter stringFromDate:now]);

    formatter.dateFormat = @"HH:mm:ss";
    NSLog(@"Time: %@", [formatter stringFromDate:now]);

    formatter.dateFormat = @"EEEE, MMMM d, yyyy 'at' h:mm a";
    NSLog(@"Friendly: %@", [formatter stringFromDate:now]);

    // Relative date formatting
    NSCalendar *calendar = [NSCalendar currentCalendar];
    NSDateFormatter *relativeFormatter = [[NSDateFormatter alloc] init];
    relativeFormatter.dateStyle = NSDateFormatterShortStyle;
    relativeFormatter.timeStyle = NSDateFormatterShortStyle;
    relativeFormatter.doesRelativeDateFormatting = YES;

    NSDate *yesterday = [NSDate dateWithTimeIntervalSinceNow:-86400];
    NSDate *tomorrow = [NSDate dateWithTimeIntervalSinceNow:86400];

    NSLog(@"Yesterday: %@", [relativeFormatter stringFromDate:yesterday]);
    NSLog(@"Tomorrow: %@", [relativeFormatter stringFromDate:tomorrow]);

    // Locale
    formatter.locale = [NSLocale localeWithLocaleIdentifier:@"fr_FR"];
    formatter.dateFormat = @"MMMM dd, yyyy";
    NSLog(@"French locale: %@", [formatter stringFromDate:now]);

    formatter.locale = [NSLocale localeWithLocaleIdentifier:@"de_DE"];
    NSLog(@"German locale: %@", [formatter stringFromDate:now]);

    // Parse from string
    formatter.dateFormat = @"yyyy-MM-dd HH:mm:ss";
    NSString *dateString = @"2024-12-25 15:30:00";
    NSDate *parsed = [formatter dateFromString:dateString];
    NSLog(@"Parsed: %@", parsed);
}

@end

// MARK: - 5. NSCalendar and Components

@interface CalendarOperations : NSObject

+ (void)demonstrateCalendar {
    NSLog(@"\n--- NSCalendar Operations ---");

    NSCalendar *calendar = [NSCalendar currentCalendar];
    NSDate *now = [NSDate date];

    // Extract components
    NSDateComponents *components = [calendar componentsInTimeZone:[NSTimeZone systemTimeZone]
                                                   fromDate:now];

    NSLog(@"Year: %ld", (long)components.year);
    NSLog(@"Month: %ld", (long)components.month);
    NSLog(@"Day: %ld", (long)components.day);
    NSLog(@"Hour: %ld", (long)components.hour);
    NSLog(@"Minute: %ld", (long)components.minute);
    NSLog(@"Second: %ld", (long)components.second);

    // Weekday
    NSLog(@"Weekday: %ld", (long)components.weekday);

    // Week of year
    NSLog(@"Week of year: %ld", (long)components.weekOfYear);

    // Specific components
    NSInteger year = [calendar component:NSCalendarUnitYear fromDate:now];
    NSInteger month = [calendar component:NSCalendarUnitMonth fromDate:now];
    NSInteger day = [calendar component:NSCalendarUnitDay fromDate:now];

    NSLog(@"Date: %ld-%02ld-%02ld", (long)year, (long)month, (long)day);

    // First day of month
    NSRange range = [calendar rangeOfUnit:NSCalendarUnitDay inUnit:NSCalendarUnitMonth forDate:now];
    NSLog(@"Days in month: %lu", (unsigned long)range.length);

    // Start of day
    NSDate *startOfDay = [calendar startOfDayForDate:now];
    NSLog(@"Start of day: %@", startOfDay);

    // End of day
    NSDate *endOfDay = [calendar dateBySettingHour:23 minute:59 second:59 ofDate:now options:0];
    NSLog(@"End of day: %@", endOfDay);

    // Week bounds
    NSDate *startOfWeek = [calendar dateFromComponents:[calendar components:NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitWeekday | NSCalendarUnitDay forDate:now]];

    components.weekday = calendar.firstWeekday;
    components.day = components.day - (components.weekday - calendar.firstWeekday);

    NSDate *weekStart = [calendar dateFromComponents:components];
    NSLog(@"Start of week: %@", weekStart);
}

@end

// MARK: - 6. Date Arithmetic

@interface DateArithmetic : NSObject

+ (void)demonstrateArithmetic {
    NSLog(@"\n--- Date Arithmetic ---");

    NSCalendar *calendar = [NSCalendar currentCalendar];
    NSDate *now = [NSDate date];

    // Add components
    NSDateComponents *addComponents = [[NSDateComponents alloc] init];
    addComponents.day = 7;
    addComponents.month = 1;

    NSDate *futureDate = [calendar dateByAddingComponents:addComponents toDate:now options:0];
    NSLog(@"Plus 1 month and 7 days: %@", futureDate);

    // Subtract components
    NSDateComponents *subtractComponents = [[NSDateComponents alloc] init];
    subtractComponents.month = -3;

    NSDate *pastDate = [calendar dateByAddingComponents:subtractComponents toDate:now options:0];
    NSLog(@"Minus 3 months: %@", pastDate);

    // Add years
    NSDateComponents *yearComponents = [[NSDateComponents alloc] init];
    yearComponents.year = 1;

    NSDate *nextYear = [calendar dateByAddingComponents:yearComponents toDate:now options:0];
    NSLog(@"Next year: %@", nextYear);

    // Last day of month
    NSDate *endOfMonth = [calendar dateByAddingUnit:NSCalendarUnitMonth value:1 toDate:now options:0];
    NSDateComponents *endOfMonthComponents = [calendar components:NSCalendarUnitYear | NSCalendarUnitMonth fromDate:endOfMonth];
    endOfMonthComponents.day = 0;
    endOfMonth = [calendar dateFromComponents:endOfMonthComponents];

    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    formatter.dateFormat = @"yyyy-MM-dd";

    NSLog(@"End of month: %@", [formatter stringFromDate:endOfMonth]);

    // Business days (simplified)
    NSDate *fiveBusinessDays = [self addBusinessDays:5 toDate:now calendar:calendar];
    NSLog(@"5 business days later: %@", [formatter stringFromDate:fiveBusinessDays]);
}

+ (NSDate *)addBusinessDays:(NSInteger)days toDate:(NSDate *)date calendar:(NSCalendar *)calendar {
    NSDate *result = date;
    NSInteger added = 0;

    while (added < days) {
        result = [calendar dateByAddingUnit:NSCalendarUnitDay value:1 toDate:result options:0];

        NSDateComponents *comps = [calendar components:NSCalendarUnitWeekday fromDate:result];

        // Skip weekends (Saturday = 7, Sunday = 1)
        if (comps.weekday != 1 && comps.weekday != 7) {
            added++;
        }
    }

    return result;
}

@end

// MARK: - 7. Time Zones

@interface TimeZoneOperations : NSObject

+ (void)demonstrateTimeZones {
    NSLog(@"\n--- Time Zone Operations ---");

    NSDate *now = [NSDate date];

    // System timezone
    NSTimeZone *systemTZ = [NSTimeZone systemTimeZone];
    NSLog(@"System timezone: %@", systemTZ.name);
    NSLog(@"Abbreviation: %@", systemTZ.abbreviation);

    // UTC timezone
    NSTimeZone *utcTZ = [NSTimeZone timeZoneWithName:@"UTC"];
    NSLog(@"UTC offset: %@", [systemTZ secondsFromGMTForDate:now] > 0 ? @"+" : @"");
    NSLog(@"Seconds from GMT: %ld", (long)[systemTZ secondsFromGMTForDate:now]);

    // Convert timezones
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    formatter.dateFormat = @"yyyy-MM-dd HH:mm:ss z";

    formatter.timeZone = utcTZ;
    NSLog(@"UTC: %@", [formatter stringFromDate:now]);

    formatter.timeZone = [NSTimeZone timeZoneWithName:@"America/New_York"];
    NSLog(@"New York: %@", [formatter stringFromDate:now]);

    formatter.timeZone = [NSTimeZone timeZoneWithName:@"Europe/London"];
    NSLog(@"London: %@", [formatter stringFromDate:now]);

    formatter.timeZone = [NSTimeZone timeZoneWithName:@"Asia/Tokyo"];
    NSLog(@"Tokyo: %@", [formatter stringFromDate:now]);

    // Available timezones
    NSArray *timezoneNames = [NSTimeZone knownTimeZoneNames];
    NSLog(@"\nAvailable timezones (first 10):");

    for (NSString *name in [timezoneNames subarrayWithRange:NSMakeRange(0, 10)]) {
        NSTimeZone *tz = [NSTimeZone timeZoneWithName:name];
        NSLog(@"  %@ (GMT%@%ldh)",
              name,
              [tz secondsFromGMT] >= 0 ? @"+" : @"",
              (long)([tz secondsFromGMT] / 3600));
    }
}

@end

// MARK: - 8. Utility Functions

@interface DateUtilities : NSObject

+ (BOOL)isToday:(NSDate *)date {
    NSCalendar *calendar = [NSCalendar currentCalendar];

    return [calendar isDateInToday:date];
}

+ (BOOL)isYesterday:(NSDate *)date {
    NSCalendar *calendar = [NSCalendar currentCalendar];

    return [calendar isDateInYesterday:date];
}

+ (BOOL)isTomorrow:(NSDate *)date {
    NSCalendar *calendar = [NSCalendar currentCalendar];

    return [calendar isDateInTomorrow:date];
}

+ (BOOL)isThisWeek:(NSDate *)date {
    NSCalendar *calendar = [NSCalendar currentCalendar];
    NSDate *now = [NSDate date];

    NSDate *startOfWeek;
    NSTimeInterval interval;

    [calendar rangeOfUnit:NSCalendarUnitWeekOfMonth
               startDate:&startOfWeek
                interval:&interval
                 forDate:now];

    return [date compare:startOfWeek] != NSOrderedAscending &&
           [date compare:[startOfWeek dateByAddingTimeInterval:interval]] != NSOrderedDescending;
}

+ (BOOL)isThisMonth:(NSDate *)date {
    NSCalendar *calendar = [NSCalendar currentCalendar];

    return [calendar isDateInThisMonth:date];
}

+ (BOOL)isThisYear:(NSDate *)date {
    NSCalendar *calendar = [NSCalendar currentCalendar];

    return [calendar isDateInThisYear:date];
}

+ (NSInteger)daysBetween:(NSDate *)from and:(NSDate *)to {
    NSCalendar *calendar = [NSCalendar currentCalendar];

    NSDateComponents *components = [calendar components:NSCalendarUnitDay
                                               fromDate:to
                                                 toDate:from
                                                options:0];

    return labs(components.day);
}

+ (void)demonstrateUtilities {
    NSLog(@"\n--- Utility Functions ---");

    NSDate *today = [NSDate date];
    NSDate *yesterday = [NSDate dateWithTimeIntervalSinceNow:-86400];
    NSDate *tomorrow = [NSDate dateWithTimeIntervalSinceNow:86400];
    NSDate *lastWeek = [NSDate dateWithTimeIntervalSinceNow:-7 * 86400];
    NSDate *lastMonth = [NSDate dateWithTimeIntervalSinceNow:-30 * 86400];

    NSLog(@"Today is today: %@", [self isToday:today] ? @"YES" : @"NO");
    NSLog(@"Yesterday is yesterday: %@", [self isYesterday:yesterday] ? @"YES" : @"NO");
    NSLog(@"Tomorrow is tomorrow: %@", [self isTomorrow:tomorrow] ? @"YES" : @"NO");
    NSLog(@"Last week is this week: %@", [self isThisWeek:lastWeek] ? @"YES" : @"NO");
    NSLog(@"Last month is this month: %@", [self isThisMonth:lastMonth] ? @"YES" : @"NO");

    NSInteger days = [self daysBetween:yesterday and:tomorrow];
    NSLog(@"Days between yesterday and tomorrow: %ld", (long)days);
}

@end

// MARK: - Main Demonstration

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        NSLog(@"=== macOS Objective-C NSDate Examples ===\n");

        // 1. Creation
        [DateCreation demonstrateCreation];

        // 2. Comparison
        [DateComparison demonstrateComparison];

        // 3. Intervals
        [DateIntervals demonstrateIntervals];

        // 4. Formatting
        [DateFormatting demonstrateFormatting];

        // 5. Calendar
        [CalendarOperations demonstrateCalendar];

        // 6. Arithmetic
        [DateArithmetic demonstrateArithmetic];

        // 7. Timezones
        [TimeZoneOperations demonstrateTimeZones];

        // 8. Utilities
        [DateUtilities demonstrateUtilities];

        NSLog(@"\n=== NSDate Examples Completed ===");
    }

    return 0;
}