NSDate Manipulation in iOS 8

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This gist accompanies the blog post NSDate Manipulation Made Easy in iOS 8.

Apple quietly introduced a whole new suite of public API methods to NSCalendar in iOS 8 titled “Calendrical Calculations”. For some reason they seemed to have forgotten to include them in the public documentation on their developer site. Fortunately, digging in to the header file in Xcode reveals lots of descriptive comments about how to use these powerful new ways of interacting with NSDate objects.

ComparingDates.m

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

NSDate *laterToday = [calendar dateByAddingUnit:NSCalendarUnitMinute
                                          value:20
                                         toDate:today
                                        options:kNilOptions];
NSComparisonResult result1 = [calendar compareDate:today
                                            toDate:laterToday
                                 toUnitGranularity:NSCalendarUnitDay];
// result1 = NSOrderedSame

NSDate *tomorrow = [calendar dateByAddingUnit:NSCalendarUnitHour
                                        value:24
                                       toDate:today
                                      options:kNilOptions];
NSComparisonResult result2 = [calendar compareDate:today
                                            toDate:tomorrow
                                 toUnitGranularity:NSCalendarUnitDay];
// result2 = NSOrderedAscending

IsDateToday.m

NSCalendar *calendar = [NSCalendar currentCalendar];

NSDate *today = [NSDate date];
[calendar isDateInToday:today];
[calendar isDateInTomorrow:today];
[calendar isDateInYesterday:today];

NextOccurrenceOfNineThirty.m

NSCalendar *calendar = [NSCalendar currentCalendar];
NSDate *nextNineThirty = [calendar nextDateAfterDate:[NSDate date] 
                                        matchingHour:9
                                              minute:30
                                              second:0
                                             options:kNilOptions];

ThreeHoursFromNow.m

NSCalendar *calendar = [NSCalendar currentCalendar];
NSDate *threeHoursFromNow = [calendar dateByAddingUnit:NSCalendarUnitHour
                                                 value:3
                                                toDate:[NSDate date]
                                               options:NSCalendarMatchNextTime];