* Calculates the major and minor tick positions.
*
* @param major_period The period between the major ticks.
- * @param offset The time at the left border of the ruler.
+ * @param offset The virtual time at the left border of the ruler.
* @param scale The scale in seconds per pixel.
* @param width the Width of the ruler.
* @param format_function A function used to format the major tick times.