The annual calendar (PT with ruthenium dial) has no buttons. All adjustments are made via the crown (rotate crown upwards to advance both date and day by 1, and rotate crown downwards to advance only the date I believe -- or maybe only the day -- I don't recall).
The perpetual calendar (titanium w/rose gold accents and same ruthenium dial as annual calendar) is shown below and works the same way except the button on the left side of the case adjusts the month. The leap year indicator is built into the month display and is visible only during the month of February each year. The 4 Februaries in each leap year cycle are displayed in the month window as "1FE," "2FE," "3FE," and finally "BFE" in a leap year ("bissextile"). It's quite ingenious.