There are numerous places where Tana"ch uses the phrase "עד היום" or "עד היום הזה" ("until\to this day"). Usually, this phrase is used regarding the names of cities, towns, etc. - occasionally, such as the law of not eating גִּיד הַנָּשֶׁה (meat from the hind of the leg) the Torah also uses the phrase "ad hayom".
What does this phrase mean? Does it mean "forever" or until the date that the person wrote that phrase?
It seems in most cases, regarding names of places, it seems to mean "forever". So was the author predicting the future?