The term "blue moon" doesn't refer to the moon actually appearing blue. It has two different meanings:

1. "Once in a blue moon" - Meaning:

This is a phrase that refers to something happening very rarely. It doesn't have anything to do with the moon's color.

2. "A second full moon in a calendar month" - Meaning:

This is the definition that's most relevant to your question. However, even with this definition, a blue moon doesn't actually have a specific time to see. It's simply the second full moon in a month.

Here's how to find out when the next "blue moon" is:

* Use a lunar calendar: You can find online lunar calendars that show the dates of full moons. Look for months with two full moons.

* Check an astronomy website: Websites like NASA, Time and Date, or EarthSky often have information about upcoming astronomical events, including blue moons.

Important note: The moon does not actually appear blue during a blue moon. It's just a name for a rare occurrence!