I have a Date column in my Sqlite database. When I put some NSDate value in it, and open the Sqlite file through graphical tools. I get some value like 530963469.705571. The corresponding date is around today or yesterday.
It's clearly not Unix epoch datestamp value. What exactly does this value mean?
I need to change this value in order to debug my app.
From the documentation
NSDate objects encapsulate a single point in time, independent of any particular calendrical system or time zone. Date objects are immutable, representing an invariant time interval relative to an absolute reference date (00:00:00 UTC on 1 January 2001).
Since sqlite does not support NSDate directly, the date is persisted as the underlying value. 530963469.705571 represents the number of seconds between 00:00:00 UTC on 1 January 2001 and the time when you created the NSDate
You can use the NSDate initialiser init(timeIntervalSinceReferenceDate:) to create an NSDate from the time interval value.
Related
I am currently creating an app where I ask the user to input a time (through datePicker) and send the user a notification every day on that time.However, I noticed that datePicker only has an NSDate object, and was wondering if there was a Time object counterpart.Also, would this Time object be a good way of storing the time, or should I convert the hour and minutes to Integers for storage?
Thanks in advance!
NSDate also contains Time information within it. You can store the exact date and time using only NSDate.
NSDate is a generic representation independent of any time zone. According to the apple docs:
NSDate objects encapsulate a single point in time, independent of any particular calendrical system or time zone. Date objects are immutable, representing an invariant time interval relative to an absolute reference date (00:00:00 UTC on 1 January 2001)
NSDate is basically the number of seconds from the reference date mentioned above.
And yes NSDate is the best way for storing time and date information in your app.
Whenever you want to display the time, use NSDateFormatter to format the date and time into any format you desire and for any Time Zone you require.
Swift 3
The NSDate class has been renamed to Date in Swift 3
This question already has answers here:
Get NSDate from NSDate adjusted with timezone
(2 answers)
Closed 6 years ago.
I need to get current time in NSDate, not swift. I tried to do this like on screenshot, but the final nsdate is in wrong timezone.
An NSDate does not have a time zone. It records an instant in time on planet Earth. It is DISPLAYED in a particular time zone.
An NSDateFormatter will convert between NSDate objects and date strings (in either direction).
If you install a time zone into your date formatter then it will convert dates to/from strings using that time zone. If you don't specify a time zone it will use the user's current time zone.
If you try to display an NSDate using the Swift print statement or NSLog then it will be displayed in UTC. Always.
The code you've posted that prints strDate, your date string you created using a date formatter, is correct. The line `print(localDate!) is meaningless.
To repeat: NSDate objects do not have a time zone. When you log them to the console, they will always be displayed in UTC. If you want to see them in your local time zone then you need to use date formatter like you are doing.
I have searched through the internet and found that [NSTimeInterval] can be set using following code.
myCalendarDay.date = [date timeIntervalSince1970];
What I don't get is why the debugger showing the values as follows.
[date] is [NSDate] type while [myCalendarDay.date] is [NSTimeInterval] type.
I was checking their values and saw that the year is way off by 31 years.
Is this correct data?
timeIntervalSince1970 returns a NSTimeInterval and represents the number of seconds that have elapsed since the first time instant of 1 January 1970, GMT.
When you store an NSDate it actually stores the number of seconds since the first instant of 1 January 2001, GMT.
You are asking the date object to give you a representation with one reference date, then you are assigning that value to another date object (most likely a core data object that has been told to use native values when generating the subclass code). It takes the time interval, and ASSUMES it is using the proper reference date.
There are 31 years between those two dates, and not so coincidentally, there are 31 years between the times in your date object, and the date in the core data instance.
If you truly want to use 1970 as your basis, you should be creating a date with dateWithTimeIntervalSince1970:.
In my program, I have an NSArray of various dates and times, stored as strings and formatted like this: #[#"07:23",#"18:09",#"13:55"];
When I use an NSDateFormatter to convert these to NSDates, the times are correct, but year/month/day information is added.
The arrays that I have created are columns of a bus schedule. Each entry is one timeslot for whatever stop the array represents. My application needs to take the current time: [NSDate date] and see which time from the array is next in sequence. I'm just trying to display when the very next bus will arrive.
I have thought of comparing each element of the array with the current date and time using -[NSDate's laterDate:], but the problem is that when I convert the strings to NSDate objects, it gives them some random day-month-year like 13:55:00 January 1st, 2001 which will always be before the current date, so my test won't work.
I can find some workarounds that are really tragically McGuyvered but I would prefer something clean.
What I want to know are these things:
Can I remove the day/month/year portion from the NSDate?
Is it possible to easily set the day/month/year of each object in my array to today without using NSDateComponents and NSCalendar? I can manipulate them as they enter the array.
Would it be easier to reformat the current date/time to match the day/month/year of the array?
Otherwise, is there a better, cleaner solution to find the next upcoming timeslot? I am open to changing the entire format from arrays if necessary.
Can I remove the day/month/year portion from the NSDate?
No. An NSDate is merely an instant in time that is some number of seconds since some reference date. Describing that instant in time as some year/month/day depends on the local calendar. For example, the "day of month" of [NSDate date] as I type this is 28 where I live but 29 for the same NSDate value in Japan.
Is it possible to easily set the day/month/year of each object in my
NSMutableArray to today? without using NSDateComponents and
NSCalendar?
No. That's what NSDateComponents is for.
Otherwise, is there a better, cleaner solution to find
the next upcoming timeslot? I am open to changing the entire format
from arrays if necessary.
Use NSCalendar's -components:fromDate: to get an NSDateComponents object that matches [NSDate date]. Replace the hour/minute/second components with an arrival time's hour/minute/second: this is an arrival time today. Add one to the day component: this is an arrival time tomorrow. (Weekend and holiday schedules cause extra complication; the weekday component may be useful.) Convert back to NSDate using NSCalendar's -dateFromComponents: and perform your date comparisons there.
I get current time or time stamp of some image. I have to change only date while the time should not be changed. For example I use [NSdate date] to get current date and time and store in an NSdate object that is "2014-01-10 09:58:47 +0000". Now change only the date part, keeping the time same as it is "2013-11-09 09:58:47 +0000"
How can I achieve that?
Convert the date into it's date components (which includes the time part), change the date part of the components to be for the new day, and create a new date based on these components.
dateByAddingDateComponents is also another way to do it.
It's all described in the Calendrical Calculations documentation.