def serialize(cls, obj, buf=None, lineLength=None, validate=True):
        """
        Serialize iCalendar to HTML using the hCalendar microformat (http://microformats.org/wiki/hcalendar)
        """

        outbuf = buf or six.StringIO()
        level = 0  # holds current indentation level
        tabwidth = 3

        def indent():
            return ' ' * level * tabwidth

        def out(s):
            outbuf.write(indent())
            outbuf.write(s)

        # not serializing optional vcalendar wrapper

        vevents = obj.vevent_list

        for event in vevents:
            out('<span class="vevent">' + CRLF)
            level += 1

            # URL
            url = event.getChildValue("url")
            if url:
                out('<a class="url" href="' + url + '">' + CRLF)
                level += 1
            # SUMMARY
            summary = event.getChildValue("summary")
            if summary:
                out('<span class="summary">' + summary + '</span>:' + CRLF)

            # DTSTART
            dtstart = event.getChildValue("dtstart")
            if dtstart:
                if type(dtstart) == date:
                    timeformat = "%A, %B %e"
                    machine = "%Y%m%d"
                elif type(dtstart) == datetime:
                    timeformat = "%A, %B %e, %H:%M"
                    machine = "%Y%m%dT%H%M%S%z"

                #TODO: Handle non-datetime formats?
                #TODO: Spec says we should handle when dtstart isn't included

                out('<abbr class="dtstart", title="{0!s}">{1!s}</abbr>\r\n'
                    .format(dtstart.strftime(machine),
                            dtstart.strftime(timeformat)))

                # DTEND
                dtend = event.getChildValue("dtend")
                if not dtend:
                    duration = event.getChildValue("duration")
                    if duration:
                        dtend = duration + dtstart
                   # TODO: If lacking dtend & duration?

                if dtend:
                    human = dtend
                    # TODO: Human readable part could be smarter, excluding repeated data
                    if type(dtend) == date:
                        human = dtend - timedelta(days=1)

                    out('- <abbr class="dtend", title="{0!s}">{1!s}</abbr>\r\n'
                        .format(dtend.strftime(machine),
                                human.strftime(timeformat)))

            # LOCATION
            location = event.getChildValue("location")
            if location:
                out('at <span class="location">' + location + '</span>' + CRLF)

            description = event.getChildValue("description")
            if description:
                out('<div class="description">' + description + '</div>' + CRLF)

            if url:
                level -= 1
                out('</a>' + CRLF)

            level -= 1
            out('</span>' + CRLF)  # close vevent

        return buf or outbuf.getvalue()
Serialize iCalendar to HTML using the hCalendar microformat (http://microformats.org/wiki/hcalendar)