Progress Development Newsletter

How Progress Stores Dates:

Basically Progress has been able to recognize and process dates anywhere from 1/1/32768 B.C.E. through 12/31/32767 C.E. Progress will also handle leap year possibilities. A leap year is any year evenly divisible by 4 (four), for example 1992, 1996, but not years ending in "00", for example 1800 and 1900. However, and one rule many people forget, is every 400 years starting with 2000 are also leap years. So February 29, 2000 is a valid date next year.

Progress stores dates internally as integers. Each numeric value incremented from 0 represents a day. The true 0 date is January 1, 4713 B.C. Since Progress stores date in this manner, the stored date is immune from Y2K since 1/1/2000 will just be another integer one greater then 12/31/1999.

Using the "-yy" Century Offset startup parameter

-yy, known as the Century parameter, sets a 100-year window where Progress supplies a "century" value when dates are entered with one or two-digits for the year. The -yy parameter, with a default of "1900", first appeared with Progress Version 5. The default in Version 7 and above is "1950". The -yy parameter specifies the beginning of a default 100-year window that will be used when displaying and storing dates.

You can also read and set the -yy century offset with the SESSION:YEAR-OFFSET handle added in Progress Version 8.2 and above.

So if you are using "-yy 1950" when entering or displaying dates in Progress, then 05/11/72 (assuming a default US date format of 'dmy') would really be May 11, 1972. 11/30/12 would be November 30, 2012. Any dates outside of the century offset range should be DISPLAYed using a format of "99/99/9999" or else Progress will display an error message. An example of where you might need this format would be in your employee table where you are storing birthdays that are prior to 1950.

Data Import and Export using Progress:

EXPORT normally dumps dates in two ways. If the date falls within the -yy 100-year window, it is dumped with a two-digit year. Version 9 of Progress has a new startup parameter, "-yr4def", which will cause the EXPORT, PUT UNFORMATTED and MESSAGE statements to use four-digit year dates, regardless of the -yy setting. Note this parameter does not affect DISPLAY or any other forms of formatted output. Using this parameter is recommended if you are exporting data to a non-Progress system, or the another Progress application with a different -yy setting.

If you are not using Version 9 yet, but want to always have the EXPORT statement force dates into four-digit year format, then there is a workaround. Simply set your -yy parameter to a value outside all the dates in your database, for example "-yy 1000" or something similar.

When using the IMPORT statement and the data file contains two-digit year values, the -yy and YEAR-OFFSET values will be applied when expanding the date. My suggestion is to make sure data files always contain four-digit years to avoid confusion.

Other things to look for:

The first thing that you should review are any external interfaces to your Progress application. Make sure you are exporting and importing four-digit years whenever possible to avoid confusion. Whenever you need to import/export a two digit year, make sure you know what assumptions are being made about the other system.

Other possible problems may be where dates are "hard-coded" in your applications. For example 01/01/01 or 12/31/99. Another problem may be if you are storing dates in CHARACTER fields. For example, some systems might store an invoice number similar to "9912130001", which might be today's first invoice. This could lead to some problems, especially with sorting and/or finding the "first" or "last" invoice.

Above all, make sure you set aside as much time as you need to test your systems. This above everything else will let you know what you will need to take care of before the century change.

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