ntp.service
<?xml version="1.0" standalone='no'?>
<!DOCTYPE service-group SYSTEM "avahi-service.dtd">
<service-group>
<name replace-wildcards="yes">NTP Zeitserver auf %h</name> ## Name
<service>
       <type>_ntp._udp</type>
       <port>123</port>
</service>
</service-group>