[hdf-forum] time data

[Mag Gam]

Good points!

We will be using UTC.

Thanks again for the great responses!

TIA


On Tue, Jun 16, 2009 at 9:48 PM, Ger van Diepen<diepen at astron.nl> wrote:
> 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 at 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...
>
>
> On Tue, Jun 16, 2009 at 8:22 AM, Ray Burkholder<ray at oneunified.net> wrote:
>> what resolution/accuracy do you need?
>>
>>> -----Original Message-----
>>> From: Mag Gam [mailto:magawake at gmail.com]
>>> Sent: Tuesday, June 16, 2009 08:27
>>> To: hdf-forum at 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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