I have two dates which I need to compare, if one is past second. That means:
date1 := Date newDay: 10 month: 12 year: 2017
date2 := Date newDay: 1 month: 1 year: 2020
So in this case date2 is past date1, so I need this to be true.
But
date1 := Date newDay: 10 month: 12 year: 2017
date2 := Date newDay: 3 month: 7 year: 2015
should return false.
Anyone got hints? Appreciate!
I guess this depends on which dialect you are using, but ANSI standard already defines < for DateAndTime which seems similar to Date. I tried your code in Pharo and Dolphin and date1 < date2 works just fine for your needs (even if Date instantiation in Dolphin is a little bit different).
Related
so here is the problem. I want to take a date from lastDate and put it to nextDate, but also add one day to the variable nextDate. Anyone know how to do that?
| lastDate nextDate |
lastDate := Date
newDay: 10
monthNumber: 5
year: 2019.
nextDate := lastDate.
HELP HERE
^nextDate
It would help to know which Smalltalk you are using.
I will use Smalltalk/X-jv branch for the examples as it is easies for me:
| lastDate nextDate |
lastDate := Date newDay: 10
month: 5
year: 2019.
nextDate := lastDate addDays: 1.
^ nextDate
To add one day you can use the #addDays: message to your lastDate.
Edit: due to comment
To add a year you can send message #addYears:
I am currently facing a weird issue. I am trying to find out in which week of a month a given Date instance lies.
My code is the following:
var calendar : Calendar {
var calendar = Calendar(identifier: .iso8601)
calendar.timeZone = .UTC
return calendar
}
func generateDate(year: Int, month: Int, day: Int) -> Date {
let dateComponents = DateComponents(year: year, month: month, day: day)
return calendar.date(from: dateComponents)!
}
print(calendar.component(.weekOfMonth, from: Date.generateDate(year: 2019, month: 12, day: 1))) // prints "0"
print(calendar.component(.weekOfMonth, from: Date.generateDate(year: 2020, month: 1, day: 1))) // prints "1"
generateDate simply generates a Date with the help of calendar. When I print the both statements I get 0 and 1 as the result. In my opinion this is wrong. I would assume I get the same value for both since both dates should be in the first week of their respective month value.
Another example would be the 2. Dec 2019, this should give the second week as well as the 6. January 2020 should also give me the second week.
Does anyone know what could be wrong here or where my mistake could be ?
This is due to the 1st day of the month falling on a sunday, try march 01, 2020 if you want confirmation.
The first week of the month is chosen by Swift according to their own standards as ISO standards do not suggest any specific implementations so the Swift team went with this. You can ask them in their forums what their reasoning behind this is Wikipedia link
The logic for .weekOfMonth seems to be that if the "first" week is less than half a week, that is 3 days, then it is considered to be week 0 and otherwise week 1. But note that this is dependent on what locale is being used, for a country like Canada that has Sunday as first day of week there is never a week 0 when running the below code. So when the first day of week is Monday .weekOfMonth will return a value between 0 and 5 but when it is Sunday the range is 1 to 6.
This can be seen running the following code in a playground
let calendar = Calendar.current
let year = 2019
print("First day of week: \(calendar.weekdaySymbols[calendar.firstWeekday - 1])")
for month in 1...12 {
print(calendar.monthSymbols[month - 1])
let first = calendar.date(from: DateComponents(year: year, month: month, day: 1))!
if let range = calendar.range(of: .day, in: .month, for: first) {
var currentWeek = -1
for day in range {
let date = calendar.date(from: DateComponents(year: year, month: month, day: day))!
let week = calendar.component(.weekOfMonth, from: date)
if week > currentWeek {
currentWeek = week
let dayOfWeek = calendar.component(.weekday, from: date)
print("Week# \(week), weekday \(calendar.weekdaySymbols[dayOfWeek - 1])")
}
}
}
}
It seems to me if you want whatever day it is on the 1st to be the first day of weekOfMonth = 1 then you need to write your own code for this
I'm trying to manipulate a date value to go back in time exactly 1 ISO-8601 year.
The following does not work, but best describes what I want to accomplish:
date_add(date '2018-01-03', interval -1 isoyear)
I tried string conversion as an intermediate step, but that doesn't work either:
select parse_date('%G%V%u',safe_cast(safe_cast(format_date('%G%V%u',date '2018-01-03') as int64)-1000 as string))
The error provided for the last one is "Failed to parse input string "2017013"". I don't understand why, this should always resolve to a unique date value.
Is there another way in which I can subtract an ISO year from a date?
This gives the corresponding day of the previous ISO year by subtracting the appropriate number of weeks from the date. I based the calculation on the description of weeks per year from the Wikipedia page:
CREATE TEMP FUNCTION IsLongYear(d DATE) AS (
-- Year starting on Thursday
EXTRACT(DAYOFWEEK FROM DATE_TRUNC(d, YEAR)) = 5 OR
-- Leap year starting on Wednesday
(EXTRACT(DAY FROM DATE_ADD(DATE(EXTRACT(YEAR FROM d), 2, 28), INTERVAL 1 DAY)) = 29
AND EXTRACT(DAYOFWEEK FROM DATE_TRUNC(d, YEAR)) = 4)
);
CREATE TEMP FUNCTION PreviousIsoYear(d DATE) AS (
DATE_SUB(d, INTERVAL IF(IsLongYear(d), 53, 52) WEEK)
);
SELECT PreviousIsoYear('2018-01-03');
This returns 2017-01-04, which is the third day of the 2017 ISO year. 2018-01-03 is the third day of the 2018 ISO year.
I am trying to get date components from a date value from an API endpoint. I need to preserve the date values as they are already adjusted for time zone. Unfortunately, I have no control over how the API returns a date value.
When I get the date value (sessionTime) from the API, it is returned as follows:
2017-12-05 08:00:00 +0000
I need to set up a local notification based on that time, however, when I try to extract components from that date object with the following code:
let notifyTime = Calendar.current.dateComponents(
[.year, .month, .day, .hour, .minute, .second], from: sessionTime)
I get this:
year: 2017 month: 12 day: 5 hour: 2 minute: 0 second: 0 isLeapMonth: false
I am six hours from GMT so it is obvious what is going on, but I wish I could prevent it and extract the date components exactly as they are. The desired output would be:
year: 2017 month: 12 day: 5 hour: 8 minute: 0 second: 0 isLeapMonth: false
Can anyone help? Thanks!
You can specify the timeZone that DateComponents uses.
Like this:
let notifyTime = Calendar.current.dateComponents(in: TimeZone.current, from: sessionTime)
LibreOffice Calc spreadsheet offers a function ISOWEEKNUM to return the standard ISO 8601 week number of the specified date.
I want the opposite.
➠ Given a standard week number, give me the date of the first day of that week (the Monday date).
Passing integers is acceptable. Also nice if able to pass a string in standard format.
Like this:
DATE_OF_ISOWEEKNUM( 2017 , 42 ) ➝ date of Monday of week 42 in week-based year 2017
DATE_OF_ISOWEEKNUM( "2017-W42" ) ➝ date of Monday of week 42 in week-based year 2017
Ideally, I would be able to pass a number 1-7 for Monday-Sunday to specify the day-of-week for which I want a date. Something like this:
DATE_OF_ISOWEEKNUM( 2017 , 42 , 1 ) ➝ date of Monday of week 42 in week-based year 2017
DATE_OF_ISOWEEKNUM( "2017-W42-1" ) ➝ date of Monday of week 42 in week-based year 2017
DATE_OF_ISOWEEKNUM( 2017 , 42 , 7 ) ➝ as above, but Sunday
DATE_OF_ISOWEEKNUM( "2017-W42-7" ) ➝ as above, but Sunday
Example:
Formula:
=DATE(B$1,1,$A4*7)+(2-WEEKDAY(DATE(B$1,1,$A4*7)))-7*(ISOWEEKNUM(DATE(B$1,1,1))=1)
Calculate the date of day (weeknumber * 7) in the year.
Correct the day to be weekday Monday.
Correct to 7 days before, if the first day of the year is in the
first ISO weeknumber.