Fix displaying when join date is unknown

website/members/templates/members/profile.html

@@ -58,7 +58,7 @@
                         {% if period.chair %}
                         <span style="text-transform:inherit;">Voorzitter: </span>
                         {% endif %}
-                        <i>{{ period.since }} - {% if period.until %}{{ period.until }}{% else %}{% trans "today" %}{% endif %}</i>
+                        <i>{% if period.since|date:'Y m d' == '1970 01 01' %}?{% else %}{{ period.since }}{% endif %} - {% if period.until %}{{ period.until }}{% else %}{% trans "today" %}{% endif %}</i>
                     <br>
                     {% endfor %}
                 </li>
@@ -68,4 +68,4 @@
     </div>
     <!-- /portfolio single content -->
 </div>
-{% endblock %}
\ No newline at end of file
+{% endblock %}