[Elyahu41]

The issue

ZmanimFormatter.formatXSDDurationTime(Duration) is documented to return an xsd:duration, but for negative durations it returns a string that isn't a valid xsd:duration.

The edge case

Any negative Duration. For example:

• Duration.ofMinutes(-75) passed directly.
• A sha'ah zmanis whose start is after its end, such as a polar day or odd custom zmanim.
• A negative offset formatted with format() when the formatter uses XSD_DURATION_FORMAT, which toXML() / toJSON() do.

What happens

The method returns Duration.toString(), and Java writes a negative duration with a sign on every field:

new ZmanimFormatter(ZoneId.of("UTC")).formatXSDDurationTime(Duration.ofMinutes(-75).minusSeconds(3));
// "PT-1H-15M-3S"

XML Schema (and ISO 8601) allows only one sign, in front of the whole value: -PT1H15M3S. So the output is rejected by javax.xml.datatype.DatatypeFactory.newDuration, by schema validation, and by other XSD / ISO 8601 parsers (for example .NET's XmlConvert.ToTimeSpan).

The fix

For a negative duration, return "-" + duration.negated().toString(). Zero and positive durations are unchanged.

Tests

ZmanimFormatterXsdDurationTest checks:

• Positive durations, zero and null are unchanged.
• -PT1H15M3S and -PT0.5S for negative durations, and that the result round-trips through DatatypeFactory.newDuration to the same value.
• format() with XSD_DURATION_FORMAT gives -PT30M.

The negative cases fail without the fix.

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🤖 Generated with Claude Code

https://claude.ai/code/session_015Er4Sx7LnKzzCbgDEatxkU