current Date and Time - NSDate - objective-c

I need to display the current Date and Time.
I have used ;
NSDate *currentDateNTime = [NSDate date];
I want to have the current date and time (Should display the system time and not GMT time).
The output should be in a NSDate format and not NSString.
for example;
NSDate *currentDateNTime = [NSDate date];
// Do the processing....
NSDate *nowDateAndTime = .....; // Output should be a NSDate and not a NSString

Since all NSDate is GMT referred, you probably want this:
(don'f forget that the nowDate won't be the actual current system date-time, but it's "shifted", so if you will generate NSString using NSDateFormatter, you will see a wrong date)
NSDate* currentDate = [NSDate date];
NSTimeZone* currentTimeZone = [NSTimeZone timeZoneWithAbbreviation:#"GMT"];
NSTimeZone* nowTimeZone = [NSTimeZone systemTimeZone];
NSInteger currentGMTOffset = [currentTimeZone secondsFromGMTForDate:currentDate];
NSInteger nowGMTOffset = [nowTimeZone secondsFromGMTForDate:currentDate];
NSTimeInterval interval = nowGMTOffset - currentGMTOffset;
NSDate* nowDate = [[NSDate alloc] initWithTimeInterval:interval sinceDate:currentDate];

Every moment in time is the same moment in time everywhere around the world —- it is just expressed as different clock times in different timezones. Therefore, you can't change the date to some other date that represents the time in your timezone; you must use an NSDateFormatter that you feed with the timezone you are in. The resulting string is the moment in time expressed in the clock time of your position.
Do all needed calculations in GMT, and just use a formatter for displaying.

Worth reading
Does [NSDate date] return the local date and time?
Some useful resources for anyone coming to this more recently:
Apple date and time programming guide do read it if you're doing anything serious with dates and times.
https://developer.apple.com/library/content/documentation/Cocoa/Conceptual/DatesAndTimes/DatesAndTimes.html#//apple_ref/doc/uid/10000039i?language=objc
Useful category on NSDate with lots of utilities does allow a ~new~ date to be generated based on an existing date.
https://github.com/erica/NSDate-Extensions
There's also a swift version of the category
https://github.com/erica/SwiftDates

You need an NSDateFormatter and call stringFromDate this method to get a string of your date.
NSDateFormatter *dateformater = [[NSDateFormatter alloc] init];
[dateformater setDateFormat:#"yyyyMMdd,HH:mm"];
NSString *str = [dateformater stringFromDate: currentDateNTime];

use this method
-(NSDate *)convertDateToDate:(NSDate *) date
{
NSDateFormatter *formatter = [[[NSDateFormatter alloc] init] autorelease];
NSDate *nowDate = [[[NSDate alloc] init] autorelease];
[formatter setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0]];
[formatter setDateFormat:#"yyyy-MM-d H:m:s"];
NSString * strdate = [formatter stringFromDate:date];
nowDate = [formatter dateFromString:strdate];
return nowDate;
}
this may return you what you want.
i hope you this may help you.

Related

Convert the exact NSString value to NSDate [duplicate]

This question already has an answer here:
returns a date an hour in the future
(1 answer)
Closed 7 years ago.
This is my code.
NSString *dateString = #"2015-06-03 02:19:37";
NSDateFormatter *formatter = [NSDateFormatter new];
[formatter setDateFormat:#"yyyy-MM-dd hh:mm:ss"];
NSLog(#"converted date = %#",[formatter dateFromString:dateString]);
The output of the code above is: "converted date = 2015-06-02 18:19:37 +0000". I know that this is because it converts the NSString with respect to GMT, but what i wanted to happen is NSDate must be 2015-06-03 02:19:37, same with dateString
I know that this is because [the NSDateFormatter] converts the NSString with respect to GMT…
No, you're wrong. NSDateFormatter defaults to using your current time zone.
What you're not understanding is that "2015-06-02 18:19:37 +0000" is the same date and time as "2015-06-03 02:19:37" (in your local time zone, which must be GMT+0800).
Also, the description that you logged is just one representation of the date. The date does not have a year, month, day-of-month, hour, minute, second, or any of that. A date object just represents a moment in time. Such moments don't have any of that and neither do NSDate objects. Only representations of moments have those things, and they are only arrived at by processing the date through a specific calendar and time zone. In any case, any given date has multiple representations. Just because the description that gets logged happens to choose a representation that you weren't expecting doesn't mean the date is wrong.
You have implicitly requested a conversion from an NSDate object to a string when you logged it. That's because logging always involves strings. The string-formatting code used by NSLog() and the %# format specifier uses the -description method. You are never going to be able to force NSDate's implementation of -description to use your time zone, so don't try.
If you really need a string representation (and you're not just debugging) and you want it in some specific time zone or otherwise want to dictate the format, don't rely on the -description method like you are. Instead, use a date formatter to convert from NSDate to an NSString explicitly, and configure the date formatter to produce the representation that you want.
But don't confuse the need to do that with the date being wrong.
What I really wanted to do is to check if the given NSDate is already past 9PM EST (-4GMT), while i'm on +8GMT timezone.
So, use NSCalendar, NSTimeZone, and NSDateComponents to construct an NSDate for 9PM EST (on the current day, I suppose you mean) and then compare the dates.
NSDate* date = /* ... */;
NSCalendar* calendar = [[NSCalendar alloc] initWithIdentifier:NSCalendarIdentifierGregorian];
calendar.timeZone = [NSTimeZone timeZoneWithName:#"America/New_York"];
NSDate* deadline = [calendar dateBySettingHour:21 minute:0 second:0 ofDate:date options:0];
if ([date compare:deadline] == NSOrderedDescending)
/* date is after deadline */;
Here I used the convenience method -dateBySettingHour:minute:second:ofDate:options: and avoided direct use of NSDateComponents. If your needs differ, you might have to convert the date to date components using the calender, modify the components, convert them back to a date, and then compare.
Use the NSDateComponents class to build the date from the information in the string. The documentation explicitly provides an example of this:
NSDateComponents *comps = [[NSDateComponents alloc] init];
[comps setDay:6];
[comps setMonth:5];
[comps setYear:2004];
NSCalendar *gregorian = [[NSCalendar alloc]
initWithCalendarIdentifier:NSGregorianCalendar];
NSDate *date = [gregorian dateFromComponents:comps];
[comps release];
NSDateComponents *weekdayComponents =
[gregorian components:NSWeekdayCalendarUnit fromDate:date];
int weekday = [weekdayComponents weekday];
call this method with your string value...
- (NSDate *)dateFromString:(NSString *)date
{
static NSDateFormatter *dateFormatter;
if (!dateFormatter)
{
dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setLocale:[[NSLocale alloc] initWithLocaleIdentifier:#"en_US_POSIX"]];
[dateFormatter setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0]];
[dateFormatter setDateFormat:#"dd-MM-yyyy"];
}
NSLog(#"Date: %#",date);
return [dateFormatter dateFromString:date];
}
RESULT : Date: 2015-06-03 02:19:37
NSString *dateString = #"2015-06-03 02:19:37";
NSDateFormatter *f = [[NSDateFormatter alloc] init];
[f setDateFormat:#"yyyy-MM-dd"];
NSDate *startDate = [f dateFromString:dateString];
You will get the NSDate here(startDate).... May this help to you.....

Objective-C – NSDateFormatter dateFromString ignore time

If I'm not interested in the time can I ignore it? I.e I have a date string that looks like this #"2012-12-19T14:00:00" but I'm only interested in getting the date (2012-12-19) but if I set NSDateFormatter like [dateFormatter setDateFormat:#"yyyy-MM-dd"]; it will return me a nil NSDate.
An NSDate object will always contain a time component as well, as it is representing a point in time — from this perspective one could argue the name NSDate is misleading.
You should create a date formatter for creating dates from string, set the time to the start of the day and use a second date formatter to output the date without time component.
NSString *dateString = #"2012-12-19T14:00:00";
NSDateFormatter *inputFormatter = [[NSDateFormatter alloc] init];
[inputFormatter setDateFormat:#"yyyy-MM-dd'T'HH:mm:ss"];
NSDateFormatter *outputFormatter = [[NSDateFormatter alloc] init];
[outputFormatter setDateStyle:NSDateFormatterShortStyle];
[outputFormatter setTimeStyle:NSDateFormatterNoStyle];
NSDate *date = [inputFormatter dateFromString:dateString];
//this will set date's time components to 00:00
[[NSCalendar currentCalendar] rangeOfUnit:NSDayCalendarUnit
startDate:&date
interval:NULL
forDate:date];
NSString *outputString = [outputFormatter stringFromDate:date];
NSLog(#"%#", outputString);
results in
19.12.12
while the format — as it is chosen by styling — will be dependent of your environment locale
all date string returns 10 characters for the date, what i mean is the date of todayy will be 2012-11-19
you can easily substring the date and use it as you want:
Example :
NSString* newDate = #"";
newDate = [[NSDate date]substringToIndex:10];
the out put will be : 2012-11-19

Why does time returned by [NSDate date] differ from my current time?

hi all
I am in India.And I have used the following code to get the current date.
[NSDate date]
it displaying the "2011-01-20 06:51:35 +0000" but actual time is "2011-01-20 12:21:35 +0000"
.Please tell me how to get the current date.
Thanks in advance
You need to use Date Formatter for this purpose.Below is the sample code for that.
NSDate *testDate=[NSDate date];
NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
[formatter setDateFormat:#"MM DD YY hh:mm"];//You can set your required format here
NSString *dt = [formatter stringFromDate:testDate];
[formatter release];
NSString *strDateTaken=dt;
Cheers
What does “actual time” mean? The current time in your time zone? Considering the time values given I’d guess that the first one is GMT and you want IST (+5:30). (See Time zones on Wikipeda.) Depends on what you want to do with the date – if you just want a formatted date and time in your current time zone, Aditya’s answer should work.
To Find Current date and difference between current date and Given date...its working code
NSDate *testDate=[NSDate date];
NSDateFormatter *formatterNew = [[NSDateFormatter alloc] init];
[formatterNew setDateFormat:#"dd-MM-yyyy HH:mm:ss "];
NSString *dt = [formatterNew stringFromDate:testDate];
NSString *strDateTaken=dt;
NSLog(#"Date=%#",strDateTaken);
[formatterNew release]; // This line can be removed if you are using ARC
NSDateFormatter *tempFormatter = [[[NSDateFormatter alloc]init]autorelease];
[tempFormatter setDateFormat:#"dd-MM-yyyy HH:mm:ss"];
NSDate *toDate = [tempFormatter dateFromString:strDateTaken];
NSLog(#"Current Date ==%#",toDate);
NSDateFormatter *tempFormatter1 = [[[NSDateFormatter alloc]init]autorelease];
[tempFormatter1 setDateFormat:#"dd-MM-yyyy HH:mm:ss"];
NSDate *startdate = [tempFormatter1 dateFromString:#"30-08-2011 16:25:00"];
NSLog(#"Last Date ==%#",startdate);
int i = [startdate timeIntervalSince1970];
int j = [toDate timeIntervalSince1970];
double X = j-i;
int days=(int)((double)X/(3600.0*24.00));
NSLog(#" Difference :%d",days);

How to set the NSDate on iPhone?

I want to ask 2 questions about the NSDate of iPhone application.
1) How to set the
NSDate *startDay to 01-01-2010 and NSDate *endDay to 31-12-2010
2) how many day between the startDay and the endDay.
What should I do? Thank you very much.
For handling dates with different formats you would need to use NSDateFormatter
NSDateFormatter *format = [[NSDateFormatter alloc] init];
[format setDateFormat:#"mm-dd-yyyy"];
To get date with specified format
NSString *dateString = [format stringFromDate:date];
To create a date from string with specified format:
NSDate *date = [format dateFromString:dateString];
NSDateFormatter documentation
To find the difference between two dates:
NSTimeInterval interval = [endDay timeIntervalSinceDate:startDay];
timeIntervalSinceDate documentation

What's the best/easiest way to compare two times in Objective-C?

I've got a string representation of a time, like "11:13 AM." This was produced using an NSDateFormatter and the stringFromDate: method.
I'd like to compare this time to the current time, but when I use the dateFromString: method to turn the string back into a date, a year, month and day are added - which I don't want. I just need to know if right now is < or > the time stored in the string.
What's going to be the best way to handle that? Thanks in advance for your help.
Instead of using the string representation, use the NSDate you got from the picker. You can convert that hour/min/sec using NSDateComponents, then also convert [NSDate date] to NSDateComponents. Compare the hours/minutes/seconds of the two sets of components.
EDIT -- use a utility function for things like this that converts the hr/min/sec components of NSDate into a secondsOfTheDay (seconds since midnight).
You can directly use two time of day values since they are both seconds since midnight. Simple integers can be easily compared and stored and manipulated. You don't have to use NSDate all the time.
//----------------------------------------------------------------------------
// extracts hour/minutes/seconds from NSDate, converts to seconds since midnight
//----------------------------------------------------------------------------
unsigned secondOfTheDay( NSDate* time )
{
NSCalendar* curCalendar = [NSCalendar currentCalendar];
const unsigned units = NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit;
NSDateComponents* comps = [curCalendar components:units fromDate:time];
int hour = [comps hour];
int min = [comps minute];
int sec = [comps second];
return ((hour * 60) + min) * 60 + sec;
}
If I understand the problem correctly, you’re using the dateFromString: method of NSDateFormatter. This is giving you the correct time, but with a default date of January 1, 1970, which is useless to compare against the current date/time.
This is easy to solve. Use setDefaultDate: to set the default date to today.
NSDate *now = [NSDate date];
NSDateFormatter *formatter = [[[NSDateFormatter alloc] init] autorelease];
[formatter setDateFormat:#"hh:mm a"];
[formatter setDefaultDate:now];
NSDate *theDate = [formatter dateFromString:#"11:13 AM"];
NSComparisonResult theResult = [theDate compare:now];
Can you reuse the string formatter that you used to create the string? So, let's say you created the string like this:
NSDateFormatter *formatter = [[[NSDateFormatter alloc] init];
[formatter setDateFormat:#"HH:mm a"];
NSString *dateAsString = [formatter stringFromDate:[NSDate date]];
You can get an NSDate like this:
NSDateFormatter *formatter = [[[NSDateFormatter alloc] init];
[formatter setDateFormat:#"HH:mm a"];
NSDate *date = [formatter dateFromString:dateAsString];
The day, month, year and timezone information will not be kept, but you'll have an NSDate object with the values of 1/1/1970 and GMT for the timezone offset.
At this point you can use the compare: (which is typically reserved for sorting operations) or the laterDate: or earlierDate: methods.
Be careful using NSDateFormatter like this, as you may run into issues with internationalization.
If you need to add information about the current date to the date you get from dateFromString:, such as the month day and year, you'll need to use NSCalendar's dateByAddingComponents:toDate:options: method.
If the string was originally created from an NSDate, then you'll want to use that original NSDate to compare against [NSDate date] using NSDate's compare: method (or some variant, such as earlierDate: or laterDate:).
You should use 24-hour based NSDateFormatter and compare as strings ("09:00am" > "08:00pm", but "09:00" < "20:00") . But in general it is right to operate with NSDate instances instead of strings