EXSLT dates-and-times seems to be broken

[mied]

I want to use the date xslt extension for some xml/xslt transformations but the implementation seems to be broken.
I use this test file to check if the date functions work:

from amara.xslt import transform

XML_DOC = """<?xml version="1.0"?>
<durations>
    <duration>P4Y8MT7H</duration>
    <duration>P17Y1MT2H</duration>
    <duration>P1Y2MT2H</duration>
</durations>"""
XSL_STYLESHEET = """<?xml version="1.0"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:date="http://exslt.org/dates-and-times">
<xsl:output method="html" omit-xml-declaration="yes" indent="yes"/>
<xsl:template match="/">
<out>
    <datetime><xsl:value-of select="date:date-time()"/></datetime>
    <date><xsl:value-of select="date:date('2000-01-02T03:04:05Z')"/></date>
    <time><xsl:value-of select="date:time('2000-01-02T03:04:05Z')"/></time>
    <year><xsl:value-of select="date:year('2000-01-02T03:04:05Z')"/></year>
    <leapyear><xsl:value-of select="date:leap-year('2000-01-02T03:04:05Z')"/></leapyear>
    <monthinyear><xsl:value-of select="date:month-in-year('2000-01-02T03:04:05Z')"/></monthinyear>
    <monthname><xsl:value-of select="date:month-name('2000-01-02T03:04:05Z')"/></monthname>
    <monthabbreviation><xsl:value-of select="date:month-abbreviation('2000-01-02T03:04:05Z')"/></monthabbreviation>
    <weekinyear><xsl:value-of select="date:week-in-year('2000-01-02T03:04:05Z')"/></weekinyear>
    <dayinyear><xsl:value-of select="date:day-in-year('2000-01-02T03:04:05Z')"/></dayinyear>
    <dayinmonth><xsl:value-of select="date:day-in-month('2000-01-02T03:04:05Z')"/></dayinmonth>
    <dayofweekinmonth><xsl:value-of select="date:day-of-week-in-month('2000-01-02T03:04:05Z')"/></dayofweekinmonth>
    <dayinweek><xsl:value-of select="date:day-in-week('2000-01-02T03:04:05Z')"/></dayinweek>
    <dayname><xsl:value-of select="date:day-name('2000-01-02T03:04:05Z')"/></dayname>
    <dayabbreviation><xsl:value-of select="date:day-abbreviation('2000-01-02T03:04:05Z')"/></dayabbreviation>
    <hourinday><xsl:value-of select="date:hour-in-day('2000-01-02T03:04:05Z')"/></hourinday>
    <minuteinhour><xsl:value-of select="date:minute-in-hour('2000-01-02T03:04:05Z')"/></minuteinhour>
    <secondinminute><xsl:value-of select="date:second-in-minute('2000-01-02T03:04:05Z')"/></secondinminute>
    <formatdate><xsl:value-of select="date:format-date('2000-01-02T03:04:05Z', 'EEE, d MMM yyyy HH:mm:ss')"/></formatdate>
    <weekinmonth><xsl:value-of select="date:week-in-month('2000-01-02T03:04:05Z')"/></weekinmonth>
    <difference><xsl:value-of select="date:difference('2000-01-01T00:00:00Z', '2000-01-02T03:04:05Z')"/></difference>
    <add><xsl:value-of select="date:add('2000-01-02T03:04:05Z', 'P1DT1H1M1S')"/></add>
    <addduration><xsl:value-of select="date:add-duration('P4DT4H4M4S', 'P1DT2H3M4S')"/></addduration>
    <sum><xsl:value-of select="date:sum(//duration)"/></sum>
    <seconds><xsl:value-of select="date:seconds('2000-01-02T03:04:05Z')"/></seconds>
    <duration><xsl:value-of select="date:duration('93784')"/></duration>
</out>
</xsl:template>
</xsl:stylesheet>"""

print transform(XML_DOC, XSL_STYLESHEET)

Runing this file fails with a stack trace. It seems like the implementation in amara/xslt/exslt/datetime.py is broken (missing imports,...).
Did I do something wrong or can somebody else confirm this?