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Why does java.time.Period#normalized() not normalize days?
What is reflection and why is it useful?Does a finally block always get executed in Java?What is a serialVersionUID and why should I use it?Why does Java have transient fields?Why is subtracting these two times (in 1927) giving a strange result?Why don't Java's +=, -=, *=, /= compound assignment operators require casting?Why is char[] preferred over String for passwords?Why is processing a sorted array faster than processing an unsorted array?Why does this code using random strings print “hello world”?Why is printing “B” dramatically slower than printing “#”?
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In the Java class java.time.Period the method normalized() has the following in its Javadoc:
This normalizes the years and months units, leaving the days unit unchanged.
The superclass' method has the following in its Javadoc:
The process of normalization is specific to each calendar system. For example, in the ISO calendar system, the years and months are normalized but the days are not, [...]
I do not have access to the actual text of ISO 8601-1:2019, and would not like to spend hundreds of [insert currency here]s on it (my guess is that normalization may be described in Part 1: Basic rules and not in Part 2: Extensions).
Could someone shed light upon why Period#normalized() does not normalize days? Does it really come directly from ISO 8601 itself, is it somewhere else specified, or is it just specific to the Java implementation?
java datetime java-time iso8601 period
edited 7 hours ago
Basil Bourque
127k36 gold badges427 silver badges600 bronze badges
asked 9 hours ago
D. KovácsD. Kovács
8255 silver badges19 bronze badges
add a comment |
In the Java class java.time.Period the method normalized() has the following in its Javadoc:
This normalizes the years and months units, leaving the days unit unchanged.
The superclass' method has the following in its Javadoc:
The process of normalization is specific to each calendar system. For example, in the ISO calendar system, the years and months are normalized but the days are not, [...]
I do not have access to the actual text of ISO 8601-1:2019, and would not like to spend hundreds of [insert currency here]s on it (my guess is that normalization may be described in Part 1: Basic rules and not in Part 2: Extensions).
Could someone shed light upon why Period#normalized() does not normalize days? Does it really come directly from ISO 8601 itself, is it somewhere else specified, or is it just specific to the Java implementation?
java datetime java-time iso8601 period
edited 7 hours ago
Basil Bourque
127k36 gold badges427 silver badges600 bronze badges
asked 9 hours ago
D. KovácsD. Kovács
8255 silver badges19 bronze badges
@Zabuza: I'm familiar with the Wikipedia page, however, it does not cover normalization of dates/periods.
– D. Kovács
8 hours ago
add a comment |
In the Java class java.time.Period the method normalized() has the following in its Javadoc:
This normalizes the years and months units, leaving the days unit unchanged.
The superclass' method has the following in its Javadoc:
The process of normalization is specific to each calendar system. For example, in the ISO calendar system, the years and months are normalized but the days are not, [...]
I do not have access to the actual text of ISO 8601-1:2019, and would not like to spend hundreds of [insert currency here]s on it (my guess is that normalization may be described in Part 1: Basic rules and not in Part 2: Extensions).
Could someone shed light upon why Period#normalized() does not normalize days? Does it really come directly from ISO 8601 itself, is it somewhere else specified, or is it just specific to the Java implementation?
java datetime java-time iso8601 period
edited 7 hours ago
Basil Bourque
127k36 gold badges427 silver badges600 bronze badges
asked 9 hours ago
D. KovácsD. Kovács
8255 silver badges19 bronze badges
In the Java class java.time.Period the method normalized() has the following in its Javadoc:
This normalizes the years and months units, leaving the days unit unchanged.
The superclass' method has the following in its Javadoc:
The process of normalization is specific to each calendar system. For example, in the ISO calendar system, the years and months are normalized but the days are not, [...]
I do not have access to the actual text of ISO 8601-1:2019, and would not like to spend hundreds of [insert currency here]s on it (my guess is that normalization may be described in Part 1: Basic rules and not in Part 2: Extensions).
Could someone shed light upon why Period#normalized() does not normalize days? Does it really come directly from ISO 8601 itself, is it somewhere else specified, or is it just specific to the Java implementation?
java datetime java-time iso8601 period
java datetime java-time iso8601 period
edited 7 hours ago
Basil Bourque
127k36 gold badges427 silver badges600 bronze badges
asked 9 hours ago
D. KovácsD. Kovács
8255 silver badges19 bronze badges
edited 7 hours ago
Basil Bourque
127k36 gold badges427 silver badges600 bronze badges
asked 9 hours ago
D. KovácsD. Kovács
8255 silver badges19 bronze badges
edited 7 hours ago
Basil Bourque
127k36 gold badges427 silver badges600 bronze badges
edited 7 hours ago
Basil Bourque
127k36 gold badges427 silver badges600 bronze badges
edited 7 hours ago
Basil Bourque
127k36 gold badges427 silver badges600 bronze badges
127k36 gold badges427 silver badges600 bronze badges
asked 9 hours ago
D. KovácsD. Kovács
8255 silver badges19 bronze badges
asked 9 hours ago
D. KovácsD. Kovács
8255 silver badges19 bronze badges
asked 9 hours ago
D. KovácsD. Kovács
8255 silver badges19 bronze badges
8255 silver badges19 bronze badges
@Zabuza: I'm familiar with the Wikipedia page, however, it does not cover normalization of dates/periods.
– D. Kovács
8 hours ago
add a comment |
@Zabuza: I'm familiar with the Wikipedia page, however, it does not cover normalization of dates/periods.
– D. Kovács
8 hours ago
@Zabuza: I'm familiar with the Wikipedia page, however, it does not cover normalization of dates/periods.
– D. Kovács
8 hours ago
@Zabuza: I'm familiar with the Wikipedia page, however, it does not cover normalization of dates/periods.
– D. Kovács
8 hours ago
add a comment |
1 Answer
1
active
oldest
votes
This is because a period of years or months is always the same amount of time (the same period) for any given date. A year is always 12 months, 12 months are always a year, thus these parts of the period can easily be normalized.
However days are variable in relation to months and years. If you have a period of 1 year, 1 month and 32 days, you cannot normalize this to 1 year, 2 months and then a fixed amount of days, because it might be 1 day, 2 days, 3 days or 4 days, depending on which date you will apply the period on.
A month can be 28, 29, 30 or 31 days. A year can be 365 or 366 days. And since a period is independent of any fixed date, there is no way to decide these relations.
Example:
2019-01-01 + 01-01-32 is 2020-03-04
2020-01-01 + 01-01-32 is 2021-03-03
2020-02-01 + 01-01-32 is 2021-04-02
2020-03-01 + 01-01-32 is 2021-05-03
As you can see the days resulting from applying the same period to different dates varies depending on the month and on if it's a leap year.
Thus it is impossible to normalize days in a period and the days are not touched when normalizing.
answered 8 hours ago
Max VollmerMax Vollmer
6,3745 gold badges21 silver badges38 bronze badges
1
That makes sense. But this means, that the "day" part of aPeriodcan be anything between Integer.MIN_VALUE and Integer.MAX_VALUE making some quite interesting constellations possible even after normalization, right? (I.e., if your API acceptsPeriodobjects, you must essentially sanity-check them?)
– D. Kovács
8 hours ago
Yeah, they can take any value. I don't see why that needs to be sanitized. A period of 500000 days is a valid period, why wouldn't it be?
– Max Vollmer
8 hours ago
Against malicious input... theoretical API for settings validity of max 2 years accepts aPeriod. Malicious input is 0 years, 1 month, 3650 days. You normalize and check year <= 2 and months accordingly. Yet, you set 10 years and a 1 month. (I know, it's a stretch, but you get the idea.)
– D. Kovács
7 hours ago
1
I would check the date I get as a result from using the period, not the period itself. But I guess it really depends on what the API is actually doing.
– Max Vollmer
6 hours ago
add a comment |
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This is because a period of years or months is always the same amount of time (the same period) for any given date. A year is always 12 months, 12 months are always a year, thus these parts of the period can easily be normalized.
However days are variable in relation to months and years. If you have a period of 1 year, 1 month and 32 days, you cannot normalize this to 1 year, 2 months and then a fixed amount of days, because it might be 1 day, 2 days, 3 days or 4 days, depending on which date you will apply the period on.
A month can be 28, 29, 30 or 31 days. A year can be 365 or 366 days. And since a period is independent of any fixed date, there is no way to decide these relations.
Example:
2019-01-01 + 01-01-32 is 2020-03-04
2020-01-01 + 01-01-32 is 2021-03-03
2020-02-01 + 01-01-32 is 2021-04-02
2020-03-01 + 01-01-32 is 2021-05-03
As you can see the days resulting from applying the same period to different dates varies depending on the month and on if it's a leap year.
Thus it is impossible to normalize days in a period and the days are not touched when normalizing.
answered 8 hours ago
Max VollmerMax Vollmer
6,3745 gold badges21 silver badges38 bronze badges
1
That makes sense. But this means, that the "day" part of aPeriodcan be anything between Integer.MIN_VALUE and Integer.MAX_VALUE making some quite interesting constellations possible even after normalization, right? (I.e., if your API acceptsPeriodobjects, you must essentially sanity-check them?)
– D. Kovács
8 hours ago
Yeah, they can take any value. I don't see why that needs to be sanitized. A period of 500000 days is a valid period, why wouldn't it be?
– Max Vollmer
8 hours ago
Against malicious input... theoretical API for settings validity of max 2 years accepts aPeriod. Malicious input is 0 years, 1 month, 3650 days. You normalize and check year <= 2 and months accordingly. Yet, you set 10 years and a 1 month. (I know, it's a stretch, but you get the idea.)
– D. Kovács
7 hours ago
1
I would check the date I get as a result from using the period, not the period itself. But I guess it really depends on what the API is actually doing.
– Max Vollmer
6 hours ago
add a comment |
This is because a period of years or months is always the same amount of time (the same period) for any given date. A year is always 12 months, 12 months are always a year, thus these parts of the period can easily be normalized.
However days are variable in relation to months and years. If you have a period of 1 year, 1 month and 32 days, you cannot normalize this to 1 year, 2 months and then a fixed amount of days, because it might be 1 day, 2 days, 3 days or 4 days, depending on which date you will apply the period on.
A month can be 28, 29, 30 or 31 days. A year can be 365 or 366 days. And since a period is independent of any fixed date, there is no way to decide these relations.
Example:
2019-01-01 + 01-01-32 is 2020-03-04
2020-01-01 + 01-01-32 is 2021-03-03
2020-02-01 + 01-01-32 is 2021-04-02
2020-03-01 + 01-01-32 is 2021-05-03
As you can see the days resulting from applying the same period to different dates varies depending on the month and on if it's a leap year.
Thus it is impossible to normalize days in a period and the days are not touched when normalizing.
answered 8 hours ago
Max VollmerMax Vollmer
6,3745 gold badges21 silver badges38 bronze badges
1
That makes sense. But this means, that the "day" part of aPeriodcan be anything between Integer.MIN_VALUE and Integer.MAX_VALUE making some quite interesting constellations possible even after normalization, right? (I.e., if your API acceptsPeriodobjects, you must essentially sanity-check them?)
– D. Kovács
8 hours ago
Yeah, they can take any value. I don't see why that needs to be sanitized. A period of 500000 days is a valid period, why wouldn't it be?
– Max Vollmer
8 hours ago
Against malicious input... theoretical API for settings validity of max 2 years accepts aPeriod. Malicious input is 0 years, 1 month, 3650 days. You normalize and check year <= 2 and months accordingly. Yet, you set 10 years and a 1 month. (I know, it's a stretch, but you get the idea.)
– D. Kovács
7 hours ago
1
I would check the date I get as a result from using the period, not the period itself. But I guess it really depends on what the API is actually doing.
– Max Vollmer
6 hours ago
add a comment |
This is because a period of years or months is always the same amount of time (the same period) for any given date. A year is always 12 months, 12 months are always a year, thus these parts of the period can easily be normalized.
However days are variable in relation to months and years. If you have a period of 1 year, 1 month and 32 days, you cannot normalize this to 1 year, 2 months and then a fixed amount of days, because it might be 1 day, 2 days, 3 days or 4 days, depending on which date you will apply the period on.
A month can be 28, 29, 30 or 31 days. A year can be 365 or 366 days. And since a period is independent of any fixed date, there is no way to decide these relations.
Example:
2019-01-01 + 01-01-32 is 2020-03-04
2020-01-01 + 01-01-32 is 2021-03-03
2020-02-01 + 01-01-32 is 2021-04-02
2020-03-01 + 01-01-32 is 2021-05-03
As you can see the days resulting from applying the same period to different dates varies depending on the month and on if it's a leap year.
Thus it is impossible to normalize days in a period and the days are not touched when normalizing.
answered 8 hours ago
Max VollmerMax Vollmer
6,3745 gold badges21 silver badges38 bronze badges
This is because a period of years or months is always the same amount of time (the same period) for any given date. A year is always 12 months, 12 months are always a year, thus these parts of the period can easily be normalized.
However days are variable in relation to months and years. If you have a period of 1 year, 1 month and 32 days, you cannot normalize this to 1 year, 2 months and then a fixed amount of days, because it might be 1 day, 2 days, 3 days or 4 days, depending on which date you will apply the period on.
A month can be 28, 29, 30 or 31 days. A year can be 365 or 366 days. And since a period is independent of any fixed date, there is no way to decide these relations.
Example:
2019-01-01 + 01-01-32 is 2020-03-04
2020-01-01 + 01-01-32 is 2021-03-03
2020-02-01 + 01-01-32 is 2021-04-02
2020-03-01 + 01-01-32 is 2021-05-03
As you can see the days resulting from applying the same period to different dates varies depending on the month and on if it's a leap year.
Thus it is impossible to normalize days in a period and the days are not touched when normalizing.
answered 8 hours ago
Max VollmerMax Vollmer
6,3745 gold badges21 silver badges38 bronze badges
answered 8 hours ago
Max VollmerMax Vollmer
6,3745 gold badges21 silver badges38 bronze badges
answered 8 hours ago
Max VollmerMax Vollmer
6,3745 gold badges21 silver badges38 bronze badges
answered 8 hours ago
Max VollmerMax Vollmer
6,3745 gold badges21 silver badges38 bronze badges
6,3745 gold badges21 silver badges38 bronze badges
1
That makes sense. But this means, that the "day" part of aPeriodcan be anything between Integer.MIN_VALUE and Integer.MAX_VALUE making some quite interesting constellations possible even after normalization, right? (I.e., if your API acceptsPeriodobjects, you must essentially sanity-check them?)
– D. Kovács
8 hours ago
Yeah, they can take any value. I don't see why that needs to be sanitized. A period of 500000 days is a valid period, why wouldn't it be?
– Max Vollmer
8 hours ago
Against malicious input... theoretical API for settings validity of max 2 years accepts aPeriod. Malicious input is 0 years, 1 month, 3650 days. You normalize and check year <= 2 and months accordingly. Yet, you set 10 years and a 1 month. (I know, it's a stretch, but you get the idea.)
– D. Kovács
7 hours ago
1
I would check the date I get as a result from using the period, not the period itself. But I guess it really depends on what the API is actually doing.
– Max Vollmer
6 hours ago
add a comment |
1
That makes sense. But this means, that the "day" part of aPeriodcan be anything between Integer.MIN_VALUE and Integer.MAX_VALUE making some quite interesting constellations possible even after normalization, right? (I.e., if your API acceptsPeriodobjects, you must essentially sanity-check them?)
– D. Kovács
8 hours ago
Yeah, they can take any value. I don't see why that needs to be sanitized. A period of 500000 days is a valid period, why wouldn't it be?
– Max Vollmer
8 hours ago
Against malicious input... theoretical API for settings validity of max 2 years accepts aPeriod. Malicious input is 0 years, 1 month, 3650 days. You normalize and check year <= 2 and months accordingly. Yet, you set 10 years and a 1 month. (I know, it's a stretch, but you get the idea.)
– D. Kovács
7 hours ago
1
I would check the date I get as a result from using the period, not the period itself. But I guess it really depends on what the API is actually doing.
– Max Vollmer
6 hours ago
1
1
That makes sense. But this means, that the "day" part of a
Period can be anything between Integer.MIN_VALUE and Integer.MAX_VALUE making some quite interesting constellations possible even after normalization, right? (I.e., if your API accepts Period objects, you must essentially sanity-check them?)– D. Kovács
8 hours ago
That makes sense. But this means, that the "day" part of a
Period can be anything between Integer.MIN_VALUE and Integer.MAX_VALUE making some quite interesting constellations possible even after normalization, right? (I.e., if your API accepts Period objects, you must essentially sanity-check them?)– D. Kovács
8 hours ago
Yeah, they can take any value. I don't see why that needs to be sanitized. A period of 500000 days is a valid period, why wouldn't it be?
– Max Vollmer
8 hours ago
Yeah, they can take any value. I don't see why that needs to be sanitized. A period of 500000 days is a valid period, why wouldn't it be?
– Max Vollmer
8 hours ago
Against malicious input... theoretical API for settings validity of max 2 years accepts a
Period. Malicious input is 0 years, 1 month, 3650 days. You normalize and check year <= 2 and months accordingly. Yet, you set 10 years and a 1 month. (I know, it's a stretch, but you get the idea.)– D. Kovács
7 hours ago
Against malicious input... theoretical API for settings validity of max 2 years accepts a
Period. Malicious input is 0 years, 1 month, 3650 days. You normalize and check year <= 2 and months accordingly. Yet, you set 10 years and a 1 month. (I know, it's a stretch, but you get the idea.)– D. Kovács
7 hours ago
1
1
I would check the date I get as a result from using the period, not the period itself. But I guess it really depends on what the API is actually doing.
– Max Vollmer
6 hours ago
I would check the date I get as a result from using the period, not the period itself. But I guess it really depends on what the API is actually doing.
– Max Vollmer
6 hours ago
add a comment |
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@Zabuza: I'm familiar with the Wikipedia page, however, it does not cover normalization of dates/periods.
– D. Kovács
8 hours ago