Learn Farsi: کلاس فرانسوی ساعت چهار عصر است. - The French class is at four in the afternoon.

In English we use the preposition at for time, but Farsi doesn't need one here. You simply use the word sâ'at (which means hour or clock) followed by the number. They are linked by a hidden e sound called the ezafe, making it sâ'at-e chahâr (literally hour of four).

How do we specify PM or in the afternoon in this sentence?

Farsi doesn't use AM or PM. Instead, you add the specific time of day right after the number. Here, asr means late afternoon. It is connected to the number four with another hidden ezafe vowel, creating a chain: sâ'at-e chahâr-e asr (literally hour of four of afternoon).

Why is the order kelâs farânsavi instead of French class?

In Farsi, the noun usually comes before the adjective. The noun kelâs (class) is linked to the adjective farânsavi (French) using the same invisible ezafe vowel e we used for the time. So you pronounce it kelâs-e farânsavi, which acts like saying class of French.

Why is the word ast at the very end of the sentence?

Farsi places the main verb at the end of the sentence. The word ast means is. So the literal word order you are reading is: Class of French hour of four of afternoon is.