[fpc-pascal] convert "epoch" to UTC

[waldo kitty]

On 1/16/2012 12:40, Sven Barth wrote:
> On 16.01.2012 17:57, waldo kitty wrote:
[TRIM]
>> looks like it should be easy to convert to pascal, too ;) just gotta
>> find out what that "floor" routine does ;)
>
> Well... I would say the same as FPC's "floor" routine (
> http://www.freepascal.org/docs-html/rtl/math/floor.html ) does ;)

hehe, exactly... and it was easy to convert, too...


function getJulianDay_Year(year:integer) : double;
var
   dYear,
   a,b,
   dResult : double;
begin
   dYear := year - 1;
   A := Floor(dYear / 100);
   B := 2 - A + Math.Floor(A / 4);
   //The use of 30.600000000000001 is to correct for floating point rounding 
problems
   dResult := Floor(365.25 * dYear) + 1721422.9 + B;
   getJulianDay_Year := dResult;
end;

function getJulianDay_SatEpoch(year:integer; dSatelliteEpoch:double) : double;
var
   dResult : double;
begin
   //Tidy up the year and put it into the correct century
   year := year mod 100;
   if (year < 57) then
     year := year + 2000
   else
     year := year + 1900;

   dResult := getJulianDay_Year(year);
   dResult := dResult + dSatelliteEpoch;

   getJulianDay_SatEpoch := dResult;
end;


with this TLE epoch number, 12013.93338171, ya feed it like so...

var
   JEpoch : double;
   DT : TDateTime;

[...]
JEpoch := getJulianDay_SatEpoch(12,013.93338171);
[...]
   if TryJulianDateToDateTime(JEpoch,DT) then
     writeln(FormatDateTime('YYYY MM DD hh:mm:ss',DT));


the above /should/ return 2012 01 14 22:24:04... i'm getting the right dates 
back but all of the times are 00:00:00 :(

do JulianDateToDateTime and TryJulianDateToDateTime not do anything with hours, 
minutes, seconds and milliseconds??

i'd give TryModifiedJulianDateToDateTime a try but the docs state that just 
trying to use that routine raises an exception... is it going to handle the 
hors, minutes, seconds, and milliseconds when it gets done or is it for some 
other julian date format??

[ aside: where/how does one report documentation errors? PadLeft says to see 
also PadLeft instead of PadRight ;) ]