This is probably a rather simple problem...
I am trying to identify the first date in a series of dates with in each case number and calculate the number of days between the rest of the date records to the first date record within each case.
the data structure is as follows.
Client_ID Transaction_date
Casenum1 Date1
Casenum1 Date2
Casenum1 Date3
Casenum1 Date4
Casenum1 Date5
Casenum2 Date1
Casenum3 Date2
Casenum4 Date3
Casenum5 Date4
Casenum6 Date5
I have tried to sort the data by case numbers in SPSS, I'm stuck on what to do with the date calculations.
The following code will first Identify the earliest date for each Client_ID and put it in a new variable, then calculate the difference in days between each date and the earliest date:
aggregate out=* mode=addvariables /break Client_ID /first_date=min(Transaction_date).
compute days_between=datediff(Transaction_date, first_date, "days").
Related
I working in google sheets. I have already formatted datetime value and separated them in two columns. Now I want to find the time elapsed between these two dates?
date1 : 04/26/21 8:25:00 AM
date2 : 05/01/21 4:46:00 PM
What formula to use in google sheets?
All you need to do is substract the two dates
=H34-G34
Then set the format to Number/Duration of the cell with the formula
Giving an example, I have 2 NSDate in the same timezone UTC
NSDate *date1 = [NSDate dateWithString:#"2019-05-31 22:00:00 +0000"];
NSDate *date2 = [NSDate dateWithString:#"2019-06-01 01:00:00 +0000"];
I want to make a function to calculate difference between them in Year, month, day ignore time part. Expect result above
Year: 0
Month: 1
Day: 1
Or another example with
NSDate *date1 = [NSDate dateWithString:#"2019-02-28 22:00:00 +0000"];
NSDate *date2 = [NSDate dateWithString:#"2020-03-01 01:00:00 +0000"];
Will get result
Year: 1
Month: 13
Day: 367
I have tried answers in this question How can I calculate the difference between two dates?
But those approach using NSTimeInterval seems not reliable because of 365 or 366 days of year and does not ignore time. Answer like
NSDateComponents *components;
NSInteger days;
components = [[NSCalendar currentCalendar] components: NSDayCalendarUnit
fromDate: date1 toDate: date2 options: 0];
days = [components day];
Give wrong result too.
You could convert each NSDate value to an NSDateComponents value using NSCalendar's componentsInTimeZone:fromDate: method. This will give you the year, month and day values for your two dates, now implement your difference algorithm, which might be:
subtract the earlier date from the larger one - you can determine that based on comparing the two NSDate values
the year difference is just simple subtraction of the year components of the NSDateComponents values
the month difference is the difference between the month components, if this is negative add 12
the day difference is similar but in the negative case you have to add the length of month, which is 28, 29, 30 or 31 - figuring which is left as an exercise :-) (NSCalendar/NSDate Methods should help here)
While this guess at your required algorithm might be wrong, whatever your algorithm you should be able to implement it based on the year, month and day components. HTH
Update
So my first guess at your algorithm was wrong, my second guess is that your three differences; years, months, days; are all meant to be independent approximations of the difference in the corresponding unit. So the year difference ignores the months, days and time; the month difference ignores the days and time; and the days difference ignores the time. This is why 31 May and 1 June are "1 month" apart - the day is ignored. This guess may also be wrong of course but here is how to do it:
order you two dates so the difference is going to be positive.
get just the year, month and day components (or get them all and then discard the others) – this will discard the time component. Use one of NSCalendar's methods to do this.
your year difference is just the difference between the year components
your month difference is the difference between your month components (which could be negative) plus 12 times your year difference
your day difference can be found using components:fromDateComponents:toDateComponents:options: requesting only the day component
[Note: be careful to use the same timezone as the original dates – this is a bit fiddly as you may need to extract it from the date strings yourself (extract the +hhmm and make a time zone). You must remember that an NSDate does not store the time zone, its just an absolute point in time (so equivalent times in different times zones produce the same NSDate value) and for your calculations you want them based on the original time zone as two times one the same day in one timezone can be on different days in a different time zone...). You can set the timezone of an NSCalendar instance or use methods which take timezones when converting from NSDate to NSDateComponents]
I have table with 2 columns and 5 rows with a date in each cell. These 16 dates comprises 8 dates ranges. I want to check if a specific date is within any one of these 8 ranges of dates. How do I create a formula for this in Excel?
You can use the IF function with the AND function:
=IF(AND(date1 <= mydate, mydate <= date2), TRUE, FALSE)
Here, mydate is the date you're looking at, and date1 and date2 are the dates to which you're comparing mydate.
I create two dates like the following:
let date1 = stringToDate("2015-02-12 12:29:29")!
let date2 = stringToDate("2015-02-11 19:18:49")!
func stringToDate(var dateString: String) -> NSDate? {
let dateFormatter = NSDateFormatter()
dateFormatter.dateFormat = "yyyy-MM-dd HH:mm:ss"
dateFormatter.timeZone = NSTimeZone(name: "UTC")
return dateFormatter.dateFromString(dateString)
}
As you can see, the two date are different and are not on the same day.
To test if two dates are on the same day, I use the following method:
func isSameDayThan(date1: NSDate, date2: NSDate) -> Bool {
let calendar = NSCalendar.currentCalendar()
calendar.timeZone = NSTimeZone(abbreviation: "GMT+10")!
return calendar.compareDate(date1, toDate: date2, toUnitGranularity: .DayCalendarUnit) == .OrderedSame
}
There I don't precise any timeZone in the calendar. The local TimeZone of my device is set to GMT+10.
In that case, isSameDayThan(date1, date2)-> true
If I change the timeZone to something inferior or equal to GMT+04, then I get isSameDayThan(date1, date2)-> false.
What I don't understand is that the result is different depending on the timeZone, but I am comparing two NSDate() and NSDate() has nothing to do with time zone if I'm not wrong.
The timezone comes into play because you compare the dates with a granularity that is timezone dependent. So you are actually comparing against the local representation of the date. The point in time model that is often used to describe NSDate doesn't know about days and weeks. From a abstract standpoint (i.e. the point in time that is the same everywhere in the universe) it actually doesn't even know about seconds.
Anyway, if you would compare with == you would obviously not need a timezone. That's the only comparison that is truly independent from the local representation. If two points in time are exactly the same they are equal. Easy.
Everything beyond a straight == comparison has to be converted into local units. Not only you have to use the correct calendar, but you have to use the correct timezone as well.
Luckily there are no calendars that have days that are shorter or longer than 24 hours. And there are no timezones that differ in seconds either. Because we know that, you can actually see if dates are within the same minute with an easy calculation. e.g.:
Int(date1.timeIntervalSince1970 / 60) == Int(date2.timeIntervalSince1970 / 60)
No calendar needed because we (currently) don't have calendars that have minutes that are not 60 seconds long. No timezone needed, because we don't have timezones with offsets that differ in the number of seconds.
But we have a few timezones that have offsets that are only fractions of an hour. For example India Time Zone which has an offset of +05:30. So starting with hours the boundaries of the granularity units are timezone dependent.
If you have two NSDates which are set to 9:25 and 9:35 UTC, they are in the same hour if you compare in any timezone that has an offset that does not differ in the number of minutes (e.g. 00 in +x:00). They are in the same hour in UTC, they are in the same hour in UTC+5:00 and UTC-5:00.
But if you compare in India Time Zone these two dates are actually in different hours. Because 9:25 UTC in IST is 2:55, and 9:35 UTC is 3:05 in IST.
In your example you are comparing to the granularity of the day. Which needs to take all timezones into account. But we can still ignore the calendar, because all calendars use days that are 24 hours long.
But if you would compare to the granularity of a week, month or year you would have to take the calendar into account as well. There are calendars that have totally different months. Just because two dates are in the same month in gregorian calendars doesn't mean that they are in the same month in hebrew calendars.
Yes, it's complicated. And that's the reason all date calculation appear so verbose. People often try to hide the complexity behind a fancy helper function. Which often leads to problems. So be aware of creation functions like isSameDay().
Each time you compare a date you have to make the decision what timezone and calendar to use. If you rely on helper functions you will miss the one instance where you should actually compare against UTC instead of the local timezone.
TL;DR: If you compare with granularity you should always set the correct calendar and the correct timezone.
Th two dates are different days in the UTC time zone. But in the GMT+10 time zone they are both the same day - February 12.
2015-02-12 12:29:29 UTC = 2015-02-12 22:29:29 UTC+10
2015-02-11 19:18:49 UTC = 2015-02-12 05:18:49 UTC+10
By Default, the comparison is done in the local time zone but your date objects were specifically created in the UTC time zone.
If you create the NSDate objects from the strings using the default time zone and compare them using the default time zone, then the dates would have two different days.
I am trying to compare the date chosen on a calendar (Kal calendar implementation) with the current date. The issue is that the current date is in MM/dd/yyyy format, whereas the Kal dates will have no leading zeroes if the month or day is below 10. Is there an easy way to retrieve the current date so that it will not have leading zeroes for the day or month if it's under 10? (The current date will actually be utilized as an attribute for saved objects, so that they can later be queried using the date selected with Kal)
example current date - 07/07/2014
example Kal date - 7/7/2014
Don't compare strings holding dates. Create actual NSDate objects, using an NSDateFormatter, and compare those. The format strings you need are "MM/dd/yyyy" for your date, however you're retrieving it, and "M/d/yyyy" for Kal's date.
I have used en_US_POSIX along with "MM/dd/yyyy" & it's Working Fine
let formatter = DateFormatter()
formatter.locale = Locale(identifier: "en_US_POSIX")
formatter.dateFormat = "MM/dd/yyyy"
https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/DataFormatting/Articles/dfDateFormatting10_4.html#//apple_ref/doc/uid/TP40002369-SW7