How to use the pelican.utils.get_date function in pelican

def get_date(data):
    """Add tzinfo"""
    res = _get_date(data)
    # assuming UTC by default
    if res.tzinfo is None:
        res = pytz.utc.localize(res)
    return res

def get_date_modified(self, page, default):
        if hasattr(page, 'modified'):
            if isinstance(page.modified, datetime):
                return page.modified
            return get_date(page.modified)
        else:
            return default