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.
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UNIX Timestamp
All dates and times, even ambiguous ones (e.g. no year), are represented internally as absolute moments in time, represented as a UNIX timestamp expressing the difference between the desired time and January 1st, 1970 00:00:00 GMT. This was only possible, because
Zend_Dateis not limited to UNIX timestamps nor integer values. The BCMath extension is required to support extremely large dates outside of the range Fri, 13 Dec 1901 20:45:54 GMT to Tue, 19 Jan 2038 03:14:07 GMT. Additional, tiny math errors may arise due to the inherent limitations of float data types and rounding, unless using the BCMath extension. -
Date parts as timestamp offsets
Thus, an instance object representing three hours would be expressed as three hours after January 1st, 1970 00:00:00 GMT -i.e. 0 + 3 * 60 * 60 = 10800.
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PHP functions
Where possible,
Zend_Dateusually uses PHP functions to improve performance.