ORA-01899: bad precision specifier

Cause: An invalid precision code was specified in a date.

Solution: Enter a valid precision code in the date format. Valid precision types are: century, year, month, day, Julian date, hours, minutes, and seconds

EX :
select ADD_MONTHS(TRUNC (TO_DATE (SYSDATE),'''Q'''),0) from dual; 

When run the above statement, we will get the below mentioned
'ORA-01899: bad precision specifier'

Solution :
select ADD_MONTHS(TRUNC (TO_DATE (SYSDATE),'Q'),0) from dual;