“It’s high time” I write this post, not to be confused with you having “a high time” reading it.

According to The Phrase Finder, the origins of “It’s high time” can be found in “the allusion to the warmest time of day – when the sun is the highest in the sky… Shakespeare used it in his Comedy of Errors, 1590.” The phrase has a different meaning than “a high time,” which means a really great time.

You could also say “high noon,” but that might confuse readers in the United States who think of “high noon” as a time in the Wild West when gunslingers purportedly met in the street for gunfights.