The time required to sharpen a samurai sword, also known as a katana, can vary depending on several factors, including the condition of the blade, the skill of the person performing the sharpening, and the tools and techniques used. Here are some general considerations:

1. Blade Condition: The time needed to sharpen a katana can depend on its current state. If the blade is only mildly dull and does not have significant imperfections, the sharpening process may be relatively quick. However, if the blade is heavily worn, has nicks or chips, or requires extensive restoration, the sharpening process can take longer.
2. Skill and Experience: The skill and experience of the person performing the sharpening play a significant role. Experienced swordsmiths or professionals who specialize in sword restoration and maintenance are likely to complete the sharpening process more efficiently and effectively. They possess the knowledge and expertise to assess the blade's condition, choose the appropriate techniques, and execute the sharpening with precision.
3. Tools and Techniques: The selection of sharpening tools and techniques can impact the time required. Different methods, such as using sharpening stones, honing rods, or power tools, may vary in terms of efficiency and the level of control they provide. Some techniques require more time and attention to detail, while others may offer quicker results.
4. Blade Size and Complexity: The size and complexity of the katana blade can affect the sharpening time. Longer blades may require more passes or adjustments to ensure even sharpening along the entire length. Swords with intricate hamon (temper line) or decorative elements may require additional care and time to preserve those features during the sharpening process.

Considering these factors, it's challenging to provide a specific time frame for sharpening a katana. In the hands of an experienced professional, sharpening a katana may take a few hours or even less for a routine sharpening. However, if the blade requires extensive restoration, repairs, or removal of significant imperfections, the process may take considerably longer, potentially spanning several days or weeks.

It's worth noting that the focus should always be on the quality and precision of the sharpening rather than rushing through the process. Maintaining the integrity of the blade and achieving the desired level of sharpness should take precedence over speed.