Let's break it down:
* Son: This is the third-person plural form of the verb "ser" (to be). It's used to indicate time.
* las: This is the definite article (the) in the feminine plural form.
* Nieves: This is the feminine plural form of "Nieve," which means "snow" in Spanish. It's a traditional way of referring to 11 o'clock.
* y: This is the conjunction "and."
* cinco: This means "five."
Therefore, the phrase literally translates to "They are the Snows and five," which means it's five minutes past the "Snows," or 11 o'clock.