time data

To easily manipulate with dates/times (e.g. subtract from each other) it is easiest to convert them to numbers. Leapyears are always a bit nasty to handle.
You have to have some reference date though (like Unix counts from 1-Jan-1970).

An important question is the time span you think it will be used for.
You could use an 8-byte floating point counting seconds from 1-Jan-2020 on. This has an accuracy of 17 digits.
So for a 20 year time span, you have 10 years of positive and negative values. 10 years is 315360000 seconds, so you have about 8 digits left for decimal seconds. Seems enough for your case, but it's up to you.

For our astronomical work we use the ModifiedJulianDate as 8-byte floating point. A class takes care of all arithmetic and so involved with it.

Another option is to use two long integer values (for seconds and nanoseconds), but the arithmetic will require a bit more work.

BTW Ho do you deal with Daylight Saving Time? Or do you record all times in UTC?

Cheers,
Ger

Mag Gam <magawake@gmail.com> 06/17/09 3:17 AM >>>

The resolution should be the same.

The accuracy should be very high...

For instance: 43.33245-43.33242

12:33:43.33245 minus 12:33:43.33242 should equal .00003

Thanks again for the response...

ยทยทยท

On Tue, Jun 16, 2009 at 8:22 AM, Ray Burkholder<ray@oneunified.net> wrote:

what resolution/accuracy do you need?

-----Original Message-----
From: Mag Gam [mailto:magawake@gmail.com]
Sent: Tuesday, June 16, 2009 08:27
To: hdf-forum@hdfgroup.org
Subject: [hdf-forum] time data

If I would like to store time series data in the x column, what is the
best data type to use?

My data looks like this:

2009-10-10 12:33:43.33242
2009-10-10 12:33:43.33245
2009-10-10 12:33:43.63433
2009-10-10 12:33:43.73242
2009-10-10 12:33:43.83242
2009-10-10 12:33:43.93242
2009-10-10 12:33:43.99443
2009-10-10 12:33:44.43242

Any thoughts?

TIA

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7 posts were merged into an existing topic: time data