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https://issues.apache.org/jira/browse/JENA-1402?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16211425#comment-16211425
 ] 

Andy Seaborne commented on JENA-1402:
-------------------------------------

Here is a translation of the setup doing the JDK operations that Jena uses; it 
gives the wrong answers as well. If this is the right way to do it, then It 
seems the JDK is not calculating subtract correctly.

{noformat}
    public static void main(String... args) throws 
DatatypeConfigurationException {
        String lex1 = "PT1M3.123S";
        String lex2 = "PT0M10.123S";
        DatatypeFactory factory = DatatypeFactory.newInstance();
        Duration dt1 = factory.newDuration(lex1);
        Duration dt2 = factory.newDuration(lex2);
        System.out.println(dt1);
        System.out.println(dt2);
        System.out.println();

        Duration dt3 = dt1.subtract(dt2);
        System.out.println(dt3);
        System.out.println();
    }
{noformat}
with

{noformat}
java version "1.8.0_111"
Java(TM) SE Runtime Environment (build 1.8.0_111-b14)
Java HotSpot(TM) 64-Bit Server VM (build 25.111-b14, mixed mode)
{noformat}


> Subtracting two xsd:Duration gives incorrect results in SPARQL query
> --------------------------------------------------------------------
>
>                 Key: JENA-1402
>                 URL: https://issues.apache.org/jira/browse/JENA-1402
>             Project: Apache Jena
>          Issue Type: Bug
>          Components: ARQ
>    Affects Versions: Jena 3.4.0
>            Reporter: Greg Albiston
>
> There is an issue when subtracting two xsd:durations that include:
> * decimal seconds
> * non-zero minutes
> * second operand has a greater number of seconds than the first operand, i.e. 
> the minutes are reduced. 
> The result is a large number of minutes and incorrect seconds.
> For example:
> Integer, Larger: "PT2M3S" - "PT1M10S"  = "PT0M53S" CORRECT
> Decimal, Smaller: "PT2M3.123S" - "PT1M1.123S" = "PT1M2.000S" CORRECT
> Decimal, Larger, Seconds: "PT0M3.123S" - "PT1M10.123S"  = "-PT1M7.000S" 
> CORRECT
> Decimal, Larger, Minutes: "PT2M3.123S" - "PT1M10.123S"  = "PT883M0.020S" 
> INCORRECT
> Decimal, Larger, Hours: "PT1H4M3.123S" - "PT0M10.123S" = "PT1H3883M0.020S" 
> INCORRECT
> Example SPARQL:
> {code:sparql}
> SELECT ?res ?op1 ?op2
> WHERE{
>    VALUES (?op1 ?op2) {
>         ("PT2M3S"^^<http://www.w3.org/2001/XMLSchema#duration> 
> "PT1M10S"^^<http://www.w3.org/2001/XMLSchema#duration>)
>         ("PT2M3.123S"^^<http://www.w3.org/2001/XMLSchema#duration> 
> "PT1M1.123S"^^<http://www.w3.org/2001/XMLSchema#duration>)
>         ("PT0M3.123S"^^<http://www.w3.org/2001/XMLSchema#duration> 
> "PT1M10.123S"^^<http://www.w3.org/2001/XMLSchema#duration>)
>         ("PT2M3.123S"^^<http://www.w3.org/2001/XMLSchema#duration> 
> "PT1M10.123S"^^<http://www.w3.org/2001/XMLSchema#duration>)
>         ("PT1H4M3.123S"^^<http://www.w3.org/2001/XMLSchema#duration> 
> "PT0M10.123S"^^<http://www.w3.org/2001/XMLSchema#duration>)
>     }
>     BIND(?op1 - ?op2 AS ?res)
> }
> {code}



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