If you use a when-indication with "ago" you clearly refer to an event in the past and you use the past tense. If you want to indicate that the opening of the new restaurant is an up-to-date fact you use the Perfect: "My parents have opened a new restaurant" without indicating a time in the past.

Many moons ago is an old-fashioned expression that means a long time ago. Moons refer to months (month derives from moon) and the expression meaning is just literal. According to Ngram its usage is from the 18th century. It appears the expression is just a popular/common way to refer to an ancient measure of time.

2023年2月22日 · Does anyone have good information on the first known usage or attribution of the phrase “the best time to plant a tree was 30 years ago, the second best time is now”, or similar concepts? According...

2011年8月11日 · It has always been my understanding that circa is properly used only when exact dates are unknown or disputed. (I will concede to my betters about the use of circa with measures. Presumably, the same rule about intentional vagueness applies.) Using circa with an exact, verified set of dates is wrong. Recently, I edited a client’s work to correct “the poet John Keats lived c. 1795–1821”.

2012年7月1日 · OP also identified another instance of (1): "I know that present perfect is related to something that happened in the past but its result is important now." For example: Manager "What about the status email?" Underling, checking logs "Yes, it has been sent. In fact it was sent three hours ago."

2013年3月18日 · Both sentences communicate the facts that you started working here twenty years ago, worked here over the course of the past twenty years, and that your status of working here has not changed. The difference is one of emphasis. The lyrics from the old song, I've been working on the railroad all the live-long day. emphasizes the continuity and ongoingness of this work. If the song lyrics were I ...

Do yesterday and one day ago refer to the same time period? If no, what is the difference?

2015年2月1日 · If the entry is part of a classification: That kid is a one-and-a-half-year-old. If the entry is describing the age of the person: That kid is one and a half years old. Both of these work, and work similarly for whole numbers: That man is a 50-year-old [person]. That man is …

2013年11月1日 · How did we come to say "yonks" meaning a long period of time? "I haven't been to the cinema in yonks." Etymonline has nothing and Oxford dictionaries has: noun: British informal: a very...

2013年4月15日 · They will convey the same meaning in a negative sentence; but in ages and other durational phrases with in (in weeks/months/years/a coon's age/donkey's years) are Negative Polarity Items and can't occur outside the scope of a negative trigger. E.g, I've known him for ages/years/a long time vs ungrammatical *I have seen him in ages/weeks/months/years/a coon's age/donkey's years.