How to formulate Unix at Delphi?

Use of f-tion
UnixStartDate: TDateTime = 25569.0;

function DateTimeToUnix(ConvDate: TDateTime): Longint;
begin
 Result := Round((ConvDate - UnixStartDate) * 86400);
end;

get : 1473978988
require 1470518278402

ShowMessage(inttostr(DateTimeToUnix(Now)));

get 10 digits when you need 13

can someone tell me f-tion
July 4th 19 at 23:59
1 answer
July 5th 19 at 00:01
DateUtils.MilliSecondsBetween(ConvDate, 0);

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