XSLT functions

boolean, concat, contains, count, current, document, 
false, file-name, last, gmtime, key, name, normalize-space, 
not, number, position, string, string-length, sum, 
system-property, starts-with, substring-after, substring-before, 
save-file, substring, time, true, translate.

The system-property function is an interface to the environment variables. Examples, system-property( 'HTTP_ACCEPT_LANGUAGE'), system-property('DOCUMENT_ROOT') and so on. If a particular environment variable is undefined empty string is returned.
The time function is a wrapper of Perl time function.
The gmtime(integer expression?) function is a wrapper of Perl gmtime function. In node-set context, it returns the result tree fragment of the form

<year>2004</year><month>1</month><day>28</day><hours>12</hours><minutes>30</minutes>
<seconds>15</seconds><weekday>4</weekday><yearday>28</yearday>

<xsl:template name="time">
<xsl:for-each select="gmtime(time()+3*3600)">
<xsl:value-of select="year"/><xsl:text>-</xsl:text>
<xsl:choose>
<xsl:when test="month>9">
<xsl:value-of select="month"/>
</xsl:when>
<xsl:otherwise>
<xsl:value-of select="concat(0,month)"/>
</xsl:otherwise>
</xsl:choose><xsl:text>-</xsl:text>
<xsl:choose>
<xsl:when test="day>9">
<xsl:value-of select="day"/>
</xsl:when>
<xsl:otherwise>
<xsl:value-of select="concat(0,day)"/>
</xsl:otherwise>
</xsl:choose><xsl:text> </xsl:text>
<xsl:choose>
<xsl:when test="hours>9">
<xsl:value-of select="hours"/>
</xsl:when>
<xsl:otherwise>
<xsl:value-of select="concat(0,hours)"/>
</xsl:otherwise>
</xsl:choose><xsl:text>:</xsl:text>
<xsl:choose>
<xsl:when test="minutes>9">
<xsl:value-of select="minutes"/>
</xsl:when>
<xsl:otherwise>
<xsl:value-of select="concat(0,minutes)"/>
</xsl:otherwise>
</xsl:choose><xsl:text>:</xsl:text>
<xsl:choose>
<xsl:when test="seconds>9">
<xsl:value-of select="seconds"/>
</xsl:when>
<xsl:otherwise>
<xsl:value-of select="concat(0,seconds)"/>
</xsl:otherwise>
</xsl:choose></xsl:for-each>
</xsl:template>