How to configure UFW to allow ntp to work?

I've enabled UFW on one of production servers with configuration: Default: deny (incoming), deny (outgoing). For NTP synchronization, I've installed ntp and it's currently running.

Can someone advise what rule should be added to UFW for NTP synchronization? I've read somewhere that udp port 123 needs to be open for ntp, but when I run ntpq -p, I get following output:

     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
 propjet.latt.ne 187.253.153.32   2 u   4d 1024    0   81.243    9.054   0.000
 ec2-107-20-168- 130.207.244.240  2 u   4d 1024    0   86.669  -23.040   0.000
 utcnist2.colora .ACTS.           1 u   4d 1024    0  298.151   86.936   0.000

which indicates that I don't need to add any ufw rule and ntp is already working?

With a simple

sudo ufw allow ntp 

You can use all services listed in /etc/services

sudo ufw allow <service name>

With the following rules-set, NTP-synchronization is working perfectly for me:

sudo ufw allow 123/udp
sudo ufw allow out 123/udp
sudo ufw allow out 53

I've allowed UDP port 123 for both incoming and outgoing traffic to NTP work. Additionally I also needed to open TCP port 53 (DNS) for outgoing traffic since /etc/ntp.conf contains domain names of NTP servers. .