The LA Fox Developer Newsletter

July 1999

Y2K Support in FoxPro (Con’t from page 7)

DateTime) field.

All versions of FoxPro provide a Date field type. All versions of

Visual FoxPro also provide a DateTime field type. FoxPro stores

Date type fields in a YYYYMMDD format as shown in Figure 1:

Figure 1. Data type storage differences

Date types use 8 bytes per field per record on disk and are

stored internally as numeric values. This size is not affected by

the settings of SET CENTURY or any input masks you might

have on a textbox for data entry to a date field. This ensures

that full, unambiguous dates are stored independent of applica-

tion logic.

Dates Stored in Code

In the Date column of Figure 1, you see how it is possible to

store ambiguous date information in code. Applications may not

correctly interpret a value. In the case of a value such as “02/16/

56”, FoxPro and \‘isual FoxPro do not know if the year refers to

1956 or 2056 (or even 1856) and must therefore make an

assumption based on various settings

Additionally, one could have a date such as “01/02/56” in which

the day and month are not easily determined. In the case of

“0 1/02/56”, the format could either be mm/dd/yy or dd/mm/yy.

Because of this, functions such as YEARQ, MONTHQ,

CTOD( ) and CTOT( ) are susceptible to date ambiguities.

Dates are stored in code as they are entered. There are several

ways to enter dates in code.

Dates entered as strings

The following example shows how a date may exist in code

when stored hard-coded as a string:

myDate “02/01156”

This is not a recommended way to store a date in code. Your

application needs to handle this value appropriately for the

application, and cannot rely on features such as System

Regional settings.

In fact, dates stored in the above format are often converted for

comparison against Date or DateTime fields as in the following

example:

myDate = “02101I56”

IF cTOD(myDate)> myDateField

ENDF

Avoid this approach to storing dates in code, as there are better

ways to store dates. Some are described below.

Dates entered as dates

When you need to store hard-coded dates in Visual FoxPro,

use the Date curly braces { } as shown in this example:

myDate = (02/01156)

When you use the Date curly braces, the value is interpreted as

a date, so Visual FoxPro stores the full date, including a 4-digit

year, in compiled code: The value is set at compile time and not

runtime. In the preceding code, notice that there is only a 2-digit

year date. When this date is compiled, FoxPro must make an

assumption about which 4-digit year date to store.

The year that FoxPro assumes for a compiled date is based on

the value of SET CENTURY. The full syntax for SET CENTURY

in Visual FoxPro 6.0 is:

SET CENTURY ON I OFF I TO (nCentury [ROLLOVER nYearfl

Over the years, FoxPro has added new features to this com-

mand, so that ambiguous years in dates stored in code can be

interpreted even more easily in the way you wish.

fEd.Note: This article was excerpted from ulargerarticle,

written by Robert Green and published the ntemct. This

article, too long to re-print in this newsletter because of space

(Con’t, page 2)

A cynic is a man who, when he smells flowers, looks

around for a coffin.

—H.L. Mencken (1 880-1 956)

It Can’t Get Any Easier.......

We’ve come up with an easy way to submit articles to the LA

Fox Developer Newsletter one that has been overlooked for

a long time.

You can submit your articles to Barry Lee at CIS# 72723,3422

on Compuserve, or brlee@earthlink.net.

These articles can be on any FoxPro-related topic, whether it

concerns a new technique you’ve discovered, a certain develop-

ment technique you may favor over others, book reviews, etc.

Editor reserves the right to edit or offer constructive comments

concerning submitted articles and accepted articles shall be

considered to be in the public domain.

The quality of this newsletter really depends on the members

that support it, not just read it. And I think we’d all be surprised

by the useful information that could be circulated around the

membership.

So

How ‘bout it?

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