Dungeons are available every month and people get quite restless waiting for it. So let’s clarify the confusion to answer the question.
When do Infinity Dungeons (Dungeon) Return Each Month?
Answer: The last 2 weeks of the monthly event.
Clarification about the Last 2 Weeks: It’s not the last 2 weeks of the month, but the last 2 weeks of the monthly event quest.
Is there any exact date when the Dungeons Return every month?
No, it’s not. Every month Kabam brings a new event quest, some last a month, some last more than a month, and some even last less than a month. So the last 2 weeks of the event quest can never be the same date each month.
Usually, Infinity Dungeons return each month around 20th, but again it can never be the same date every month.
I hope this answer the question and it is applicable each month until Kabam decides to stop the Infinity Dungeons return or make any changes.