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Dates and times

XSLT 1.0 had no date type at all — you sliced date strings with substring and hoped. 2.0/3.0 bring the full XML Schema date/time types into XPath, with real arithmetic and a flexible formatting function. This is one of the clearest "impossible in 1.0, trivial now" wins.

The types

xs:date, xs:dateTime, xs:time, plus the two duration types xs:dayTimeDuration and xs:yearMonthDuration. You get the current values from functions, or cast a string:

<xsl:variable name="today"  select="current-date()"/>      <!-- 2025-03-14 -->
<xsl:variable name="now"    select="current-dateTime()"/>
<xsl:variable name="issued" select="xs:date(invoice/@date)"/>

Arithmetic

Subtracting two dates gives a duration; adding a duration to a date gives a date. It just works, time zones and leap years included:

<!-- how many days until the invoice is due? -->
<xsl:variable name="age" select="current-date() - xs:date(invoice/@date)"/>
<xsl:value-of select="days-from-duration($age)"/>

<!-- 30 days after issue -->
<xsl:value-of select="xs:date(invoice/@date) + xs:dayTimeDuration('P30D')"/>

Comparisons (<, >, =) work on dates directly, so sorting and filtering by date need no string trickery:

<xsl:for-each select="cd[xs:integer(year) ge 1985]">…</xsl:for-each>

Formatting: format-date

format-date, format-dateTime, and format-time turn a typed value into a string using a picture string of [component] markers:

<xsl:value-of select="format-date(current-date(), '[D1] [MNn] [Y0001]')"/>
<!-- 14 March 2025 -->

<xsl:value-of select="format-dateTime(current-dateTime(), '[H01]:[m01]:[s01]')"/>
<!-- 09:07:42 -->

The common components:

Marker Produces
[Y] / [Y0001] year / zero-padded to 4 digits
[M] / [M01] month number / 2-digit
[MNn] / [MNn,3-3] month name / abbreviated to 3 letters
[D] / [D1] / [D01] day of month
[FNn] weekday name (Monday…)
[H01] / [h] hour, 24- / 12-hour
[m01] [s01] minutes, seconds
[P] a.m./p.m.

Language and calendars

A fifth argument selects the language: format-date($d, '[FNn] [D] [MNn]', 'fi', (), ()) yields Finnish weekday and month names where the processor supports them. The same picture-string mechanism powers format-number for numeric output.

Components without formatting

When you just want one field as a number, the *-from-* accessors are simpler than a picture string:

year-from-date($d)    month-from-date($d)    day-from-date($d)
hours-from-dateTime($dt)   minutes-from-dateTime($dt)   seconds-from-dateTime($dt)
timezone-from-dateTime($dt)

For the weekday, there is no *-from-* accessor — use a picture string: format-date($d, '[F]') gives the day-of-week number, [FNn] the name.

Where to go next