Learn Italian: Questo mese ha ventotto giorni. - This month has twenty-eight days.

When you combine a "tens" number like venti (twenty) with a number starting with a vowel, like uno (one) or otto (eight), you drop the last vowel of the tens number. So, venti + otto becomes ventotto.

Mese ends in "-e". How do I know if it's masculine or feminine?

Nouns ending in "-e" can be either masculine or feminine in Italian, so you just have to memorize their gender as you learn them. A big clue in this sentence is the word questo (this), which is the masculine singular form. If mese were feminine, the sentence would start with "questa".

Is "this" always translated as questo?

No, questo works like an adjective and has to match the gender and number of the noun it describes. Because mese (month) is masculine and singular, we use questo. If it were a feminine noun like settimana (week), you would use questa settimana.

Do you pronounce the "h" in ha?

No, the letter "h" is always completely silent in Italian. You pronounce ha exactly like "ah". The "h" is only written there so you know it's the verb "has" (from avere) and not the word meaning "to" or "at" (a).