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The Dating Files

By Steve Hammond

Inside VESOFT covers tips and techniques you can use with VESOFT’s products, especially MPEX.

By Steve Hammond

Synchronicity is defined by Webster’s as the coincidence of events that seem to be meaningfully related, conceived in Jungian theory as an explanatory principle on the same order as causality. (I’m okay up until the comma, but when we get into “Jungian theory” I kinda glaze over.)

I can’t tell you how many times I have completed an Inside Vesoft column and within days found myself using the exact command or procedure I discussed in the column. It happened just last month when I needed to alter several spool files and used the ALTSPOOLFILE command.

This was slightly different, because I needed to select by a range of dates. I had to dig into the back of the manual to the Appendix to look over some of the date functions. There I realized the vast number of date operators and functions offered in MPEX and its companions. No one really worried about dates until less than 10 years ago when the turn of the millennium was looming, but we’ve always been able to do any number of functions with dates in MPEX.

We all know that TODAY is a date function - I regularly run:

%YESPURGE LOG####.PUB.SYS(accdate<TODAY-60) to clear all the log files older than 60 days off my system. But you can do a lot more when it comes to calculating and comparing dates. (You can test these commands using the CALC command, so you can check it before deleting an entire account.)

%calc today-1
04/04/20

Now that date looks funny. That’s because the date returned is in the YYMMDD format. If I tell it I want to create the date (CDATE) in a month/date/year format, I need to:

%calc cdatemdy(04/19/04-1)
04/18/04

Of course, you can do addition and even differences between dates:

%calc 06/25/04-02/29/04
117, $75, %165, "...u"

Here we see that the difference between June 25th and February 29th of this year is 117 days. Wait a minute - that output is not what we expected! Using CALC, if the result is an integer, it will be displayed in decimal, hexadecimal, octal and ASCII representation of the 4 bytes with periods replacing the junk/unprintable characters.

And what’s data manipulation if you can’t do boolean?

%calc (04/20/04=03/20/04)
FALSE
or
%calc (04/20/04<>03/20/04)
TRUE

Of course you can do the standard greater than, less than, equal to, less than or equal and greater than or equal.
You can even do MIN, MAX and BETWEEN functions on dates:

%calc MIN (04/21/04,03/22/04,09/22/01)
09/22/01
%calc MAX (04/21/04,03/22/04,09/22/01)
04/21/04
%calc BETWEEN (04/21/04,03/22/04,09/22/01)
FALSE

As you can see BETWEEN is a boolean function, determining if the first date is between the second and the third - and as you can see in this instance, it is not.

If you need to extract certain segments of a date, there are functions - DATEYEAR gives you the two-digit year from a date, DATEYEAR4 extracts the four-digit year, DATEMONTH AND DATEDAY provide the obvious and DATEDAYOFWEEK gives the day of the week:

%calc DATEYEAR(04/21/04)
4, $4, %4, "...."
%calc DATEYEAR4(04/21/04)
2004, $7D4, %3724, "...."
%calc DATEMONTH (05/26/01)
5, $5, %5, "...."
%calc DATEDAY(05/26/01)
26, $1A, %32, "...."
%calc DATEDAYOFWEEK(05/26/01)
7, $7, %7, “....”

In the last case, May 26, 2001 fell on a Saturday (1 is Sunday, 2 is Monday, etc.)
In my last job, where Julian date was used regularly, this came in handy

%calc DAYOFYEAR(04/21/04)
112, $70, %160, "...p"

Julian date, as defined in most applications, is the number of the day in the year - January 1st is 1, December 31st is 365 or 366 this year. As an aside, in my limited Unix experience, I was struck that it was odd the definition of a Julian date on that system was the number of seconds since some seemingly arbitrary, but no doubt significant date in the past — oh well.

The function CDATE is really expanded into three other simpler commands, all involving conversion of dates:

%calc CDATEMDY (87/01/15)
01/15/87
%calc CDATEYMD (04/26/99)
99/04/26
%calc CDATEDMY (04/15/02)
15/04/02
So you can easily convert one date format to another.
It’s not uncommon to need to determine if a date is valid:
%calc VALIDDATE("06/25/2003","MDY")
TRUE
%calc VALIDDATE("02292004","MDY")
TRUE
%calc VALIDDATE("022903","MDY")
FALSE

As you can see, it works with or without slashes, on two- or four-digit years and it recognizes valid leap year days. The quotes in there are important — I learned the hard way — had a job blow up at an inopportune time because I forgot the quotes.

So, MPEX lets you deal with dates better than my college roommate, but that’s a story for another day.

The only Jung that Steve Hammond, who works for a professional association in Washington, DC, knows is a middle relief pitcher for the Philadelphia Phillies!