Sak is the white storm, the third of the four colour-marked months. White is the colour of the north in the Maya directional scheme, and sak also carries the sense of bright, clean and artificial, so the month name has a range in Mayan that a single English word does not reproduce.
The eleventh month sits in the second half of the eighteen and, like all the full months, runs twenty days from its seating. Since a full month is exactly the length of the day-sign cycle, its seating always carries the same Tzolk'in day sign as every other month seating in the same year, which is the Year Bearer of that year, and a reader who knows the bearer can derive the day sign of any date in the year from the Haab position alone.
That derivation is a genuine convenience rather than a curiosity, and it is one reason the Calendar Round is workable in the head. What it does not give is the day number, since the thirteen Tzolk'in numbers and the 365 days of the Haab share no common factor and every number can therefore fall on every Haab position over the course of the Round.
It is worth adding that this convenience is a property of the eighteen full months only. The five days of the Wayeb break the twenty-day alignment, so the rule holds within a year and not across the seam, and it is precisely the break that makes the year advance to the next bearer. A structure that repeated exactly would produce no year names at all.