Re: Say what - take a look at this site on info for NanoSail-D2

From: George Roberts (
Date: Mon Nov 29 2010 - 15:03:57 UTC

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    From: "Kevin Fetter" <>
    > It says NanoSail-D2 was launched on 20 November, 2010, but it
    > decayed on 31 December, 1969
    Many (most?) times on computers are stored as seconds since jan 1, 1970 at 
    0:00.  In java usually milliseconds since the same date.  Most of these 
    values are stored as integers that can be negative or positive although the 
    intent is (usually) to never have negative values.  Despite this there are 
    lots of time/date functions that will display a time of -1 as dec 31, 1969.
    I suspect the database that stores this information is not using standard 
    sql dates but instead "epoch" dates (seconds since 1970) and that someone 
    put a -1 in this database field.  So probably if it told you what *time* the 
    satellite decayed it would have said dec 31, 1969 11:59 pm.
    Programmers often use 0 or -1 to store an "unknown" state (rather than have 
    a separate variable).
    - George Roberts
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