Have a wonderful day. I love [your] smile is an English equivalent of 'Avere un giorno meraviglioso. Amo [il tuo, or tu] sorriso'. The infinitive 'avere' means 'to have'. The masculine indefinite article 'uno'* means 'a, one'. The masculine noun 'giorno' means 'day'. The masculine adjective 'meraviglioso' means 'marvelous, wonderful'. The verb 'amo' means '[I] am loving, do love, love'. The masculine noun 'sorriso' means 'smile'. All together, they're pronounced 'ah-VEH-reh oon JOHR-noh MEH-rah-vee-LYOH-soh AH-moh sohr-REE-soh'.
"They're having a wonderful time" or "You all are having a wonderful time" are two equivalents of the literally-translated-from-English-into-Italian phrase Hanno un periodo meraviglioso.
Specifically, the verb hanno may mean "(they) are having, do have, have" or "(formal plural you all) are having, do have, have." The masculine singular definite article un means "a, one." The masculine noun periodo means "time, time period." The masculine adjective meraviglioso means "marvelous, wonderful."
The pronunciation will be "AHN-noh oon pey-REE-oh-doh MEY-rah-vee-LYOH-soh" in Italian.
Hanno un gran giorno in Italian means "They're having a great day" or "(formal) You are having one great day!" in English.
Un giorno così in Italian means "a day like this" in English.
Buon giorno, maestro! in Italian means "Hello, teacher (or master)!" in English.
Nipote! Buon giorno! in Italian means "Good morning nephew!" in English.
L'ultimo giorno di lavoro in Italian means "the last day of work" in English.
"How was the day?" in English is Com'è stato il giorno?in Italian.
"Have a blessed day!" in English is Giorno benedetto! in Italian.
Avere un gran bel giorno in Italian means "to have a great, beautiful day" in English.
Buon giorno, Buona notte, Arrivederci! in Italian is "Have a nice day, Have a nice night, Goodbye!" in English.
Yes it does.
"Good day!" is a literal English equivalent of the Italian phrase Buon giorno! The masculine singular adjective and noun also translate into English as "Nice day!" The pronunciation will be "bwon DJOR-no" in Italian.
"Giorno del cibo italiano"
"You will come back someday!" in English is Un giorno tornerai! in Italian.