Re: Recording and looking up dates, when day-wide precision is required
Re: Recording and looking up dates, when day-wide precision is required
- Subject: Re: Recording and looking up dates, when day-wide precision is required
- From: Florijan Stamenkovic <email@hidden>
- Date: Tue, 30 Dec 2008 11:19:06 -0400
- Delivered-to: email@hidden
- Delivered-to: email@hidden
On Dec 30, 2008, at 06:03, Lachlan Deck wrote:
Hi there,
On 30/12/2008, at 7:47 PM, Andrew Lindesay wrote:
I _think_ (correct me if I'm wrong) Florijan would like to store a
logical date rather than a timestamp. For example, he would like
to store the date 2008-09-28. The requirement being that the same
date is applicable to all timezones because it is composited from
year/month/day and is thus independent of timezones.
An example where this might be useful is to store birthdays.
Right - I think it was Florijan's more elaborate description that
confused me :-) I thought he was saying he wanted the date to be
presented according to the user's local timezone whilst at the same
time he was talking about this need. So I wasn't clear on his aims.
Plus, perhaps you were thinking of a web-app scenario, and that's not
what I am doing. I am working on a JC app, where dates are
transferred to and from the client machine in raw form. So, all the
parsing and formatting happens on the client machine, which could be
anywhere.
For example, a birthday is 1980-08-08. If I should decide to live
in Munich for a while (I presently live in Auckland) then the same
birthday applies, but if I stored it as a timestamp then it would
have shifted to another day while I live in Munich. Hence the
difficulty storing these things as timestamps.
Depends when you want your present ;-)
So if you're storing dates in the database (as opposed to
timestamps) you'll have to normalise them prior to storage. For
display you'll need a custom formatter.
As I stated before, a point in time defined with the time of 11:30
GMT, whichever date, formats into the same date (textually) in
virtually all timezones. However, I still have some confusion about
this. If I look at a map of the world, virtually all places on the
planet are in the -11 +12 offset range:
http://www.yeswatch.com/timekeeper/images/manual/time-zone-map-large.jpg
However, Java provides different results. For example, the "New
Zealand Standard Time" is at +13. Something I do not understand at
all (since geographically it is partly in +11, partly in +12). So,
apparently this method does not cover 100% of the globe. Bummer. I
guess that a custom formatter would be necessary to cover also those
time zones (-12, +13, +14). Or I can just ignore the New Zealanders :P
F
btw, sorry for the confusion, I should have indicated that this is a
JC scenario, and perhaps you could have seen what I was trying to say.
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