Time Functions

Namespace

The Time Functions ontology’s namespace is https://w3id.org/time-fn#.

The preferred namespace prefix is tfn:.

The current version of the ontology specified in this document is 1.0.0.

A Turtle version of the ontology is available here.

1. Introduction

The Time Functions ontology offers a set of functions tailored to manage time literals in RDF and SPARQL. It addresses the need for manipulating time periods, including those without a designated timezone, and facilitates the retrieval of inclusive or exclusive bounds for these periods.

This functionality enables the comparison and sorting of time literals in SPARQL queries by mapping time periods (e.g., xsd:gYear, xsd:gYearMonth, and xsd:date) to specific xsd:dateTime values with an explicit timezone.

These functions are particularly useful for working with time periods that may include partial time literals, such as xsd:gYear, xsd:gYearMonth, and xsd:date, and for handling floating times, i.e., time literals that lack a specified timezone.

In addition to mapping time periods to specific xsd:dateTime values based on their inclusive or exclusive bounds, a function is also provided to assign a default timezone to time literals without a specified timezone.

When using these functions on a date "2025-06-30"^^xsd:date, the inclusive lower bound is interpreted as "2025-06-30T00:00:00.000+14:00"^^xsd:dateTime, and the inclusive upper bound is interpreted as "2025-06-30T23:59:59.999+-4:00"^^xsd:dateTime. The exclusive lower bound is interpreted as "2025-06-29T23:59:59.999+14:00"^^xsd:dateTime, and the exclusive upper bound is interpreted as "2025-07-01T00:00:00.000-14:00"^^xsd:dateTime. When binding a default timezone "+02:00" to a time literal without an explicit timezone, the date "2025-06-30"^^xsd:date becomes "2025-06-30+02:00"^^xsd:date, and the time literal "2025-06-30T09:00:00.000"^^xsd:dateTime becomes "2025-06-30T09:00:00.000+02:00"^^xsd:dateTime.

1.1. Function signatures and descriptions

Each function in the Time Functions ontology is defined in this document according to a similar standard proforma as defined in XPath and XQuery Functions and Operators 3.1: Function signatures and descriptions.

Each function definition follows the structure:

tfn:function-name($parameter-name as parameter-type, ...) as return-type

Where:

• tfn:function-name is the name of the function.

• $parameter-name is the name of the parameter.

• parameter-type is the type of the parameter, such as xsd:dateTime, xsd:date, or xsd:gYear.

• return-type is the type of the return value, typically xsd:dateTime.

2. Time Functions

This section lists all the functions defined in the Time Functions ontology operating on the XML Schema Part 2: Datatypes Second Edition date and time types xsd:dateTime, xsd:date, xsd:gYearMonth, and xsd:gYear.

2.1. tfn:periodMinInclusive

Summary

Returns the inclusive lower bound of a time period.

Signature

tfn:periodMinInclusive(
    $period as xsd:dateTime | xsd:date | xsd:gYearMonth | xsd:gYear
) as xsd:dateTime

Properties

This function is deterministic, context-independent, and focus-independent.

Rules

The function tfn:periodMinInclusive takes a time period as input and returns the inclusive lower bound of that period as an xsd:dateTime. The input $period can be of type xsd:dateTime, xsd:date, xsd:gYearMonth, or xsd:gYear.

If the input $period is an xsd:dateTime and has a timezone, the function returns the same value. Otherwise, if the input is an xsd:dateTime but has no explicit timezone, the input is interpreted as a period of -14 hours to +14 hours around the given dateTime, and the inclusive lower bound is returned as the xsd:dateTime with a timezone of UTC+14:00.

If the input $period is an xsd:date, it is interpreted as a period from the start of that date (00:00:00.000) to the end of that date (23:59:59.999), and the inclusive lower bound is returned as an xsd:dateTime with the given timezone or UTC+14:00 if no timezone is specified.

If the input $period is an xsd:gYearMonth, it is interpreted as a period from the start of that month (00:00:00.000 on the first day) to the end of that month (23:59:59.999 on the last day), and the inclusive lower bound is returned as an xsd:dateTime with the given timezone or UTC+14:00 if no timezone is specified.

If the input $period is an xsd:gYear, it is interpreted as a period from the start of that year (00:00:00.000 on January 1st) to the end of that year (23:59:59.999 on December 31st), and the inclusive lower bound is returned as an xsd:dateTime with the given timezone or UTC+14:00 if no timezone is specified.

Examples

2.2. tfn:periodMaxInclusive

Summary

Returns the inclusive upper bound of a time period.

Signature

tfn:periodMaxInclusive(
    $period as xsd:dateTime | xsd:date | xsd:gYearMonth | xsd:gYear
) as xsd:dateTime

Properties

This function is deterministic, context-independent, and focus-independent.

Rules

The function tfn:periodMaxInclusive takes a time period as input and returns the inclusive upper bound of that period as an xsd:dateTime. The input $period can be of type xsd:dateTime, xsd:date, xsd:gYearMonth, or xsd:gYear.

If the input $period is an xsd:dateTime and has a timezone, the function returns the same value. Otherwise, if the input is an xsd:dateTime but has no explicit timezone, the input is interpreted as a period of -14 hours to +14 hours around the given dateTime, and the inclusive upper bound is returned as the xsd:dateTime with a timezone of UTC-14:00.

If the input $period is an xsd:date, it is interpreted as a period from the start of that date (00:00:00.000) to the end of that date (23:59:59.999), and the inclusive upper bound is returned as an xsd:dateTime with the given timezone or UTC-14:00 if no timezone is specified.

If the input $period is an xsd:gYearMonth, it is interpreted as a period from the start of that month (00:00:00.000 on the first day) to the end of that month (23:59:59.999 on the last day), and the inclusive upper bound is returned as an xsd:dateTime with the given timezone or UTC-14:00 if no timezone is specified.

If the input $period is an xsd:gYear, it is interpreted as a period from the start of that year (00:00:00.000 on January 1st) to the end of that year (23:59:59.999 on December 31st), and the inclusive upper bound is returned as an xsd:dateTime with the given timezone or UTC-14:00 if no timezone is specified.

Examples

2.3. tfn:periodMinExclusive

Summary

Returns the exclusive lower bound of a time period.

Signature

tfn:periodMinExclusive(
    $period as xsd:dateTime | xsd:date | xsd:gYearMonth | xsd:gYear
) as xsd:dateTime

Properties

This function is deterministic, context-independent, and focus-independent.

Rules

The function tfn:periodMinExclusive takes a time period as input and returns the exclusive lower bound of that period as an xsd:dateTime. The input $period can be of type xsd:dateTime, xsd:date, xsd:gYearMonth, or xsd:gYear.

If the input $period is an xsd:dateTime and has a timezone, the function returns the same value. Otherwise, if the input is an xsd:dateTime but has no explicit timezone, the input is interpreted as a period of -14 hours to +14 hours around the given dateTime, and the exclusive lower bound is returned as the xsd:dateTime with a timezone of UTC+14:00.

If the input $period is an xsd:date, it is interpreted as a period from the start of that date (00:00:00.000) to the end of that date (23:59:59.999), and the exclusive lower bound is returned as an xsd:dateTime with the given timezone or UTC+14:00 if no timezone is specified.

If the input $period is an xsd:gYearMonth, it is interpreted as a period from the start of that month (00:00:00.000 on the first day) to the end of that month (23:59:59.999 on the last day), and the exclusive lower bound is returned as an xsd:dateTime with the given timezone or UTC+14:00 if no timezone is specified.

If the input $period is an xsd:gYear, it is interpreted as a period from the start of that year (00:00:00.000 on January 1st) to the end of that year (23:59:59.999 on December 31st), and the exclusive lower bound is returned as an xsd:dateTime with the given timezone or UTC+14:00 if no timezone is specified.

Examples

2.4. tfn:periodMaxExclusive

Summary

Returns the exclusive upper bound of a time period.

Signature

tfn:periodMaxExclusive(
    $period as xsd:dateTime | xsd:date | xsd:gYearMonth | xsd:gYear
) as xsd:dateTime

Properties

This function is deterministic, context-independent, and focus-independent.

Rules

The function tfn:periodMaxExclusive takes a time period as input and returns the exclusive upper bound of that period as an xsd:dateTime. The input $period can be of type xsd:dateTime, xsd:date, xsd:gYearMonth, or xsd:gYear.

If the input $period is an xsd:dateTime and has a timezone, the function returns the same value. Otherwise, if the input is an xsd:dateTime but has no explicit timezone, the input is interpreted as a period of -14 hours to +14 hours around the given dateTime, and the exclusive upper bound is returned as the xsd:dateTime with a timezone of UTC-14:00.

If the input $period is an xsd:date, it is interpreted as a period from the start of that date (00:00:00.000) to the end of that date (23:59:59.999), and the exclusive upper bound is returned as an xsd:dateTime with the given timezone or UTC-14:00 if no timezone is specified.

If the input $period is an xsd:gYearMonth, it is interpreted as a period from the start of that month (00:00:00.000 on the first day) to the end of that month (23:59:59.999 on the last day), and the exclusive upper bound is returned as an xsd:dateTime with the given timezone or UTC-14:00 if no timezone is specified.

If the input $period is an xsd:gYear, it is interpreted as a period from the start of that year (00:00:00.000 on January 1st) to the end of that year (23:59:59.999 on December 31st), and the exclusive upper bound is returned as an xsd:dateTime with the given timezone or UTC-14:00 if no timezone is specified.

Examples

2.5. tfn:bindDefaultTimezone

Summary

Bind a default timezone to a time literal if no explicit timezone was indicated in the time literal.

Signature

tfn:bindDefaultTimezone(
    $timeLiteral as xsd:dateTime | xsd:date | xsd:gYearMonth | xsd:gYear,
    $defaultTimezone as xsd:string
) as xsd:dateTime | xsd:date | xsd:gYearMonth | xsd:gYear

Properties

This function is deterministic, context-independent, and focus-independent.

Rules

The function tfn:bindDefaultTimezone takes a time literal and a default timezone as input and returns the time literal with the default timezone bound to it if no explicit timezone was indicated in the time literal. The input $timeLiteral can be of type xsd:dateTime, xsd:date, xsd:gYearMonth, or xsd:gYear. The input $defaultTimezone is a string representing the default timezone, typically in the format +HH:MM or -HH:MM, or Z for UTC.

If the input $timeLiteral has a timezone, the function returns the same value. Otherwise, if the input is an xsd:dateTime, xsd:date, xsd:gYearMonth, or xsd:gYear without a timezone, the function binds the default timezone to the time literal and returns it as an xsd:dateTime, xsd:date, xsd:gYearMonth, or xsd:gYear with the specified timezone.

Examples