isWeekend

Oracle:
select case when mod(TO_CHAR(sysdate), 'J' in (5, 6) then 'T' else 'F' end from DUAL;

Ms-SQL:
select case when Datepart(dw, getdate()) + @@datefirst in (7, 8, 14) then 'T' else 'F' end

Are there better ways to escape from NLS hell ?

Oracle - Microsoft (1:1) here.