Hello Vishal,
I was just able to got that working in a HANA Calculayed Column please use below.
if( "ReportingMonth"=midstr(string(now()),6,2) And "ReportingYear"=midstr(string(now()),1,4),
midstr(string(now()),9,2),
(if(int(midstr(string(now()),6,2))=12,
'31',
Midstr(String(adddays(Date((midstr(string(now()),1,4))+'-'+string(int(midstr(string(now()),6,2))+1)+'-01'),-1)),9,2))))
Replace ReportingMonth and ReportingYear with your database field.
Regards
Niraj