Short Answer 
The U.S. Constitution’s 22nd Amendment limits presidents to two terms, which cannot be changed even during national emergencies. While the president gains certain powers during such times under the National Emergencies Act, neither Congress nor the Supreme Court allows modifications to the presidential term length.
Step 1: Understand the Presidential Term Limits
The U.S. Constitution, specifically the 22nd Amendment, clearly defines the maximum length of a presidential term. This amendment limits a president to only two terms in office, ensuring a regular and democratic transition of power. Consequently, even in instances of national emergencies, the rules governing presidential terms remain firmly in place.
Step 2: Explore Presidential Powers During National Emergencies
During a declared national emergency, the president gains certain special powers as outlined in the National Emergencies Act of 1976. However, it’s essential to recognize that these powers do not extend to modifying the term length of the presidency. Thus, while the president can respond to emergencies with heightened authority, they cannot extend their time in office.
Step 3: Recognize the Role of Congress and the Supreme Court
Both Congress and the Supreme Court play significant roles in limiting presidential powers during emergencies. Congress has the ability to define and restrict presidential actions, while the Supreme Court typically upholds these constraints. For instance, the ruling in Youngstown Sheet & Tube Co. v. Sawyer serves as a reminder that even when challenges arise, the president cannot overstep their constitutional bounds, such as altering electoral processes or delaying elections.