Union Government
(1) An election to fill a vacancy caused by the expiration of the term of office of President shall be completed before the expiration of the term. (2) An election to fill a vacancy occurring by reason of death, resignation or removal shall be held as soon as possible after, and in no case later than six months from, the date of occurrence of the vacancy; the person so elected is entitled to a full five-year term from the date they enter office.
A presidential election must be completed before a term ends when the vacancy is expected (a normal end of term), and within six months when the vacancy is unexpected (death, resignation, or removal) - either way, ensuring the office is filled promptly and without long gaps.
If a sitting President were to die in office, the Constitution requires a new presidential election to be completed within six months, with the Vice-President acting as President in the meantime under Article 65.