- Add parseRelativeExpression() to detect pattern: attr+/-duration
- Add resolveDateValue() to resolve absolute or relative dates
- Add applyDateAttribute() helper for date attributes with relative support
- Track attribute order in Modifier struct (AttributeOrder field)
- Refactor Apply() and ApplyToNew() to process attrs in order
- Support chaining: due:mon scheduled:due-3d wait:scheduled-1d
- Support addition and subtraction: due+1y, wait-2d
- Add comprehensive test suite for relative expressions
- Error if referencing undefined date attribute
- All 38+ tests passing
- Create DateParser struct with configurable base time and week start
- Add placeholder methods for new parsing features
- Implement time-of-day parsing foundation (splitDateTime, parseTimeOfDay)
- Maintain backward compatibility with existing ParseDate() function
- Update tests to use new DateParser API
- All 33 existing tests passing