delphi 日期转换字符串函数

function GetStrDate(datestr:string):string; //20190101000021  返回 2019-01-01 00:00:21
var
 str : string;
begin
  str := copy(datestr,1,4)+'-'+ copy(datestr,5,2)+'-'+copy(datestr,7,2)+' '+ copy(datestr,9,2)+':'+copy(datestr,11,2)+':' +copy(datestr,13,2) ;
  result:=str;
end;

function GetDateStr(datestr:string):string;  //2019-01-01 00:00:21 返回 20190101000021
var
 str : string;
begin
  str := copy(datestr,1,4)+ copy(datestr,6,2)+copy(datestr,9,2)+ copy(datestr,12,2)+copy(datestr,15,2)+copy(datestr,18,2) ;
  result:=str;
end;