So, for a recap of this very important plot point:
Cyrus arrived in Thantopolis in the middle of the night, AKA past midnight.
Despite this, he wasn't tired.

Helene told Cyrus sometime before Ch4 that he came to Thantopolis on June 1st.
So it was 1 or 2 AM let's say when he met Helene in the throne room.

However, Cyrus discovered he never woke up on the 31st, or he would have marked his calendar. So what happened between the night on the 30th and the wee hours of the 1st??

Well... I promise we'll get that answer by the end of the comic!