To solve this problem, we need to determine the day of the week on February 8, 2004, given that February 8, 2005, was a Tuesday.

Step 1: Identify if 2004 is a leap year

• A year is a leap year if it is divisible by 4. However, if it is divisible by 100, it must also be divisible by 400.
• 2004 is divisible by 4, and since it's not divisible by 100, it is a leap year. Therefore, 2004 has 366 days.

Step 2: Calculate the day difference between Feb 8, 2005, and Feb 8, 2004

• Since 2004 is a leap year, the number of days from February 8, 2004, to February 8, 2005, is 366 days.

Step 3: Calculate the day of the week for Feb 8, 2004

• Since 366 days are equivalent to 52 weeks and 2 days (because $366 \div 7 = 52$ weeks and $2$ days).
• Therefore, February 8, 2004, was 2 days before February 8, 2005.

If February 8, 2005, was a Tuesday, then:

• One day before Tuesday is Monday.
• Two days before Tuesday is Sunday.

Conclusion:

The day of the week on February 8, 2004, was Sunday.

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Would you like more details or have any questions about this calculation? Here are 5 related questions to explore further:

1. How do you calculate the day of the week for any given date?
2. What is the difference between a leap year and a regular year?
3. How do leap years affect calendar calculations?
4. How can modular arithmetic be used to solve day-of-the-week problems?
5. How can you determine the day of the week for historical events?

Tip: When solving date-related problems, always remember to account for leap years, as they can shift days of the week by an extra day.