ORA-01861: literal does not match format string

In last few days I had a problem with some SQL queries in Oracle database. I won't give you this particular SQL query which has ended with error which you can find in the header of this post, but i will give solution! :)

Suppose that your SQL queries use data in format for instance YYYY-MM-DD, so before them execute below command which specifies the default date format which can be used in TO_CHAR and TO_DATE functions :

alter session  set NLS_DATE_FORMAT='YYYY-MM-DD';

Reference :
[1] Docs Oracle NLS_DATE_FORMAT