The methods are grouped by how they act on the date and whether they need addtional information. You can change the start date, number to add, and enddate. Rather than using several buttons there is just one per section. Similarly, there's just one field for the number of days, weekdays, weeks, months, and years to add to the start date. The number entered is used as the appropriate units for the method.
I hope you find this useful.
* The results were rounded to two decimals using