How to determine if an NSDate is today?

Question

How to check if an NSDate belongs to today?

I used to check it using first 10 characters from [aDate description]. [[aDate description] substringToIndex:10] returns string like "YYYY-MM-DD" so I compared the string with the string returned by [[[NSDate date] description] substringToIndex:10].

Is there more fast and/or neat way to check?

Thanks.

Answer 1

You can compare date components:

NSDateComponents *otherDay = [[NSCalendar currentCalendar] components:NSYearCalendarUnit|NSMonthCalendarUnit|NSDayCalendarUnit fromDate:aDate];
NSDateComponents *today = [[NSCalendar currentCalendar] components:NSYearCalendarUnit|NSMonthCalendarUnit|NSDayCalendarUnit fromDate:[NSDate date]];
if([today day] == [otherDay day] &&
   [today month] == [otherDay month] &&
   [today year] == [otherDay year]) {
    //do stuff
}

Edit:

I like stefan's method more, I think it makes for a cleaner and more understandable if statement:

NSCalendar *cal = [NSCalendar currentCalendar];
NSDateComponents *components = [cal components:(NSYearCalendarUnit|NSMonthCalendarUnit|NSDayCalendarUnit) fromDate:[NSDate date]];
NSDate *today = [cal dateFromComponents:components];
components = [cal components:(NSYearCalendarUnit|NSMonthCalendarUnit|NSDayCalendarUnit) fromDate:aDate];
NSDate *otherDate = [cal dateFromComponents:components];

if([today isEqualToDate:otherDate]) {
    //do stuff
}

Answer 2

You could also check the time interval between the date you have, and the current date:

[myDate timeIntervalSinceNow]

This will give you the time interval, in seconds, between myDate and the current date/time.

Link.

Answer 3

I would try to get todays date normalized to midnight and the second date, normalize to midnight then compare if it is the same NSDate.

From Apple example here's how you normalize to midnight today's date, do the same for the second date and compare:

NSCalendar * gregorian = [[NSCalendar alloc]
                               initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents * components =
    [gregorian components:
                 (NSYearCalendarUnit|NSMonthCalendarUnit|NSDayCalendarUnit)
                 fromDate:[NSDate date]];
NSDate * today = [gregorian dateFromComponents:components];

Answer 4

This could probably be reworked as an NSDate category, but i used:

// Seconds per day (24h * 60m * 60s)
#define kSecondsPerDay 86400.0f

+ (BOOL) dateIsToday:(NSDate*)dateToCheck
{
    // Split today into components
    NSCalendar* gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
    NSDateComponents* comps = [gregorian components:(NSYearCalendarUnit|NSMonthCalendarUnit|NSDayCalendarUnit|NSHourCalendarUnit|NSMinuteCalendarUnit|NSSecondCalendarUnit) 
                                        fromDate:[NSDate date]];

    // Set to this morning 00:00:00
    [comps setHour:0];
    [comps setMinute:0];
    [comps setSecond:0];
    NSDate* theMidnightHour = [gregorian dateFromComponents:comps];
    [gregorian release];

    // Get time difference (in seconds) between date and then
    NSTimeInterval diff = [dateToCheck timeIntervalSinceDate:theMidnightHour];
    return ( diff>=0.0f && diff<kSecondsPerDay );
}

(However, comparing the two date strings as in the original question almost feels 'cleaner'..)