Two Digit Date Windows

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I was reading some of the items in the two banking posts and wanted to start a new thread to discuss what I see will be a potential problem with some Y2K "solutions".

Many companies are employing "windowing" techniques to attempt make software Y2K compliant by "assuming" that dates ending in two digits (ie. 98, 99, 00, 01 ,02) have the appropriate century and millenium.

I have heard this referred to as "windowing" or "epochs".

What happens when different companies chose different base dates for their windows? (What if company A choses 30 as the dividing line (ie. 2029, but 1930) and company B choses 40 (or 20) as the dividing line?

Will they communicate these "windows" to one another? Probably not? Then make incorrect assumptions on dates? You bet.

So, even software that is "Y2K Compliant" may not be "fixed".

Glen Austin

-- Glen Austin (gdaustin@aol.com), December 21, 1998

Answers

Glen,

Yes, that is an example of all the little secondary issues that make Y2K more complex than it appears at first.

-- No Spam Please (anon@ymous.com), December 21, 1998.


The objective of windowing is to generate a result date that has a valid year, you may decide that different dates in be treated differently than dates that are normally current, eg transaction date. It is possible to have a date routine to which you provide a variable "window" value, this technique is known as a sliding window.

When you provide dates to another company on an interchange file you normally provide the result date in an agreed format, the window value being used as a parameter to the code.

Of course windowing only has a finite life, it is normally considered to be a quick and nasty fix to the system to give it more life before its replaced. The windowing should give you plenty of time to do that.

-- Richard Dale (rdale@figroup.co.uk), December 21, 1998.


To rephrase the first para:

The objective of windowing is to generate a result date that has a valid year, you may decide that various types of date field are be treated differently eg you may have dates that are normally current, eg transaction date, or dates that may be way into the past, eg dates of birth. You may want to apply a unique "window" value to each one. To do so it is possible to have a date routine to which you provide a variable "window" value. This technique is known as a sliding window.

-- Richard Dale (rdale@figroup.co.uk), December 21, 1998.


"What happens when different companies chose different base dates for their windows?" Heck, what happens when the same company chooses different base dates (technically known as "pivot points" in the Y2K remediation biz)? This is what Microsoft has done with their EXCEL and ACCESS products, which are often used with the same data!!! And depending on what release level of either product is being used, this can have different pivot points, still!

-- Jack (jsprat@eld.net), December 21, 1998.

My company is using 68 as the pivot year and any application using a different year must obtain a waiver to do so. With justification, other applications may use a different year. It basically comes down to what the interfaces do, the type of dates transmitted, and the century information. Credit cards are using windowing but I'm unsure of the pivot year, so our interfaces with credit card companies "remain unchanged" in that the date is not expanded to YYYY. It could be a problem but the application owners must design the interface based on the upstream or downstream requirements.

Troll Maria

-- Maria (anon@ymous.com), December 21, 1998.



This "windowing" or "epoching" is how Microsoft claims it is compliant with its "Office" and other products. NOT!!

Microsoft sucks.

-- POffed (POed@microsoftsucks.bla), December 21, 1998.


Hello 'Troll Maria'! Thanks for the input! Are you sure you want the 'troll' title? I don't mind changing my name to make it easier on everyone. Say, 'Mari', since my husband calls me that already?

-- Maria (encelia@mailexcite.com), December 21, 1998.

You can be certain that within a given large company there will be "window" conflicts at times. Personally, I thought windowing was a bad idea from the start. It doesn't make code changes easier (actually its harder). Its done to avoid data conversions on a massive scale. To me, its a Faustian bargain.

-- RD. ->H (drherr@erols.com), December 21, 1998.

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