Thirty in French, “trente,” holds mathematical significance as the end and beginning of decades. Historically, it marks “Les Trente Glorieuses,” a prosperous period in France, and the “Thirty Years’ War.” Idiomatically, “être dans la trentaine” indicates someone in their 30s. Personally, the age of 30 often signifies a period of introspection and growth, with both challenges and opportunities.