| hours since 1-1-1 [message #44865] |
Tue, 26 July 2005 18:53  |
qian
Messages: 3
Registered: July 2005
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Junior Member |
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Dear IDL users:
Is there an IDL function/program that converts the unidata time unit to
more readable format?
For example: hours since 1-1-1 17338824 -> Jan 1 1979.
Thanks,
Qian
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| Re: hours since 1-1-1 [message #45031 is a reply to message #44865] |
Thu, 04 August 2005 15:09  |
Mark Hadfield
Messages: 783
Registered: May 1995
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Senior Member |
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Reimar Bauer wrote:
>
> We prefer Julian Seconds which were initial defined by Ray Sterner at
> JHUapl.
Personally, I prefer Modified Julian Days...
MJD = JD - 2,400,000.5
...because the values are smaller and they avoid the tricky "integer
value at noon" thing. Also because they are used in William Thompson's
very nice CDS library.
However RSI prefers Julian Days and IDL provides various functions to
deal with it. Also, there are the calendar formats, which make labelling
axes very straightforward and can't easily be replaced by the user.
So my recommendation to anyone who wants to deal with date-time data in
IDL and doesn't have special requirements (like very high precision,
leap seconds and the like) remains "use Julian Dates".
--
Mark Hadfield "Kei puwaha te tai nei, Hoea tahi tatou"
m.hadfield@niwa.co.nz
National Institute for Water and Atmospheric Research (NIWA)
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