ORA-01861: literal does not match format string
 *Cause:  Literals in the input must be the same length as literals in
  the format string (with the exception of leading whitespace).  If the
  "FX" modifier has been toggled on, the literal must match exactly,
  with no extra whitespace.
 *Action: Correct the format string to match the literal.

• Do not rely on implicit format (NLS_DATE_FORMAT, NLS_DATE_LANGUAGE)
  
• Always apply an explicit format on TO_DATE and TO_CHAR(datetime)
  
• TO_DATE on a DATE data often leads to this error