JD2SS1970:

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   Converts a Julian Date to seconds since 00:00:00 GMT, Jan. 1, 1970.

   Since version 7.
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   Form:
   s = JD2UTC( jD );
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   Inputs
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   jD         Julian date

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   Outputs
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   s          Seconds since 00:00:00 GMT, Jan. 1, 1970.

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