|
|
|
|
|
|
|
2. Apparent difficulty. There is a general perception that date/time functions are not difficult to design or write. In some cases, this is true. Often, a "one-shot" need situation becomes a pleasant challenge, with the consequence that "rolling your own" is not perceived as a problem. |
|
|
|
|
|
|
|
|
3. Multiplicity of standards. A large number of calendars and formats for date/time expressions are in use. Despite the use of scientific standards for defining time and a large degree of acceptance of these definitions for the purposes of commerce and technology, the actual usage of date and time for ordinary daily social purposes varies considerably. |
|
|
|
|
|
|
|
|
Several consequences of this lack of a standard set of procedures and data structures are: |
|
|
|
|
|
|
|
|
1. Fragmented solution set. The actual corpus of solutions to common date/time application problems is badly fragmented. Particular individuals solve particular aspects of particular problems. General solutions to common problems are often missing altogether, because no one has addressed them. As a consequence, convoluted stand-alone solutions to individual problems have been developed in cases where an extremely simple solution that makes use of the utility functions available in a common tool kit already exists. |
|
|
|
|
|
|
|
|
2. Duplication of effort. The same problems have been solved over and over again. The waste of effort is enormous. |
|
|
|
|
|
|
|
|
3. Error. In many cases, date/time functions contain some surprising quirks. A large number of published and accepted solutions in this area are simply incorrect. In many cases, the range of validity of a published solution is misunderstood and the solution is misapplied. In many cases, knowledge of an algorithm is inadequate and must be supplemented by an historical knowledge of the situations in which the rules were violated in actual practice or simply never applied. |
|
|
|
|
|
|
|
|
In some cases, the apparent simplicity of date/time code is only that apparent. Date/time issues are often a trap for the unwary or careless. Once embedded in countless applications, subtle errors require huge amounts of time and money to discover and correct. |
|
|
|
|
|
|
|
|
1.4
Organization of the Book |
|
|
|
|
|
|
|
|
The general organization of the SCDTL material is described in the following section. |
|
|
|
|
|
|
|
|
1.4.1
Structure of the Book |
|
|
|
|
|
|
|
|
The book is organized by chapters. These chapters fall into four major groups: |
|
|
|
|
|