暇なので勉強も兼ねてDelphiで。

function Hoge: Boolean;
var
　StartTime, EndTime, CurrTime: TDateTime;
begin
　StartTime := StrToTime('23:00:00');
　EndTime := StrToTime('1:00:00');
　CurrTime := Time;

　if (EndTime < StartTime) then
　begin
　　EndTime := EndTime + 1;
　　if (CurrTime < EndTime) then CurrTime := CurrTime + 1;
　end;
　Result :=(CurrTime >= StartTime) and (CurrTime <= EndTime);
end;