People won’t know where the message comes from, they’ll just hear your voice as though you were standing next to them. Everyone hears it at the same time. The message is not translated into anyone’s native language, everyone hears it exactly as you say it. The maximum length is 6 of your breaths.
“I will reappear in one year’s time.” With the subsequent breaths saying the same phrase in the next four spoken world languages, then use the last breath to say it in R’lyehian.