How to subscribe sun

I think it is easy but I have no Idea. I have a lot experience in MQTT, I have a weather station I send values to HA and I if subdisplay showing part of these values via MQTT subscribtion to HA. But these are all self defined topics.
But no I like to display if it is day or night on my subdisplay but I need the topic I have tos subscribe.

Thanks for any hint

OK I found out I just have to publish it first
I think I found how to publish sunset or sunraise, but that means that when i start my MQTT client I have to wait till the next event. Can I publish or query a current state