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From: jrl@images1.Waterloo.NCR.COM (john Latala)
Newsgroups: comp.sys.handhelds
Subject: time formats for HP28s
Message-ID: <920@ncrwat.Waterloo.NCR.COM>
Date: 24 Jul 90 01:41:25 GMT
Sender: news@ncrwat.Waterloo.NCR.COM
Reply-To: john.Latala@Waterloo.NCR.COM
Organization: NCR Canada Ltd, Waterloo, Ontario, Canada.
Lines: 35
Keywords:

I was working on a program that did time/date manipulations. I ended up
with a list of dates and wanted to sort them. This is where the problem
started. 

I'm using a HP28 variations of a number of time routines that I used on
my HP41. I modified the routines to follow the HP41 date/time format.
Times are in the format HH.MMSSTT and dates are in the format MM.DDYYYY.

Sorting dates in the MM.DDYYYY format doesn't work! January 1, 1991
(01.011991) is before July 1, 1990 (07.011990)!

I was thinking about converting to something like YYYY.MMDD or even
YYYYMMDD.

After a bit more poking around I thought maybe going to a binary version
might be a litte neater, something like #YYYYMMDDhhmmssttd. This format
doesn't look to bad because I can get a complete date/time into one
number, which is kind of a nice idea.

Any other formats that may be more suitable to manipulation?

In planning for when it happens how does the HP48 store/handle
dates/times?

My current routines actually keep the time as GMT. I then have a
variable called 'TZ' that stores the number of (1/8192)'ths of a second
that the local time zone is shifted from GMT. 

My date/time routines get the current tick count, add the 'TZ' variable
and convert the result to either a date or a time. 

Do any other calculators besides the HP's offer this kind of date/time
manipulation?
--
john.Latala@Waterloo.NCR.COM