Why is there only one class Zend_Date for handling dates and times in Zend Framework?

Many languages split the handling of times and calendar dates into two classes. However, Zend Framework strives for extreme simplicity, and forcing the developer to manage different objects with different methods for times and dates becomes a burden in many situations. Since Zend_Date methods support working with ambiguous dates that might not include all parts (era, year, month, day, hour, minute, second, timezone), developers enjoy the flexibility and ease of using the same class and the same methods to perform the same manipulations (e.g. addition, subtraction, comparison, merging of date parts, etc.). Splitting the handling of these date fragments into multiple classes would create complications when smooth interoperation is desired with a small learning curve. A single class reduces code duplication for similar operations, without the need for a complex inheritance hierarchy.