In any grid menu layout (such as the calendar), the Left and Right keys will often do something special instead of opening the previous/next top-level menu as they usually do. This is no great problem; the same is true for submenu titles, for example. What is important is that you can quickly navigate out of the grid, back to a point where Left and Right *do* open the previous/next top-level menu.
In this particular example, if a date in the first week of the month is highlighted, pressing Up once or (once bug 740821 is fixed) twice should return to a point where Left and Right will navigate to the previous/next top-level menu.
In any grid menu layout (such as the calendar), the Left and Right keys will often do something special instead of opening the previous/next top-level menu as they usually do. This is no great problem; the same is true for submenu titles, for example. What is important is that you can quickly navigate out of the grid, back to a point where Left and Right *do* open the previous/next top-level menu.
In this particular example, if a date in the first week of the month is highlighted, pressing Up once or (once bug 740821 is fixed) twice should return to a point where Left and Right will navigate to the previous/next top-level menu.