Given that January 1, 2007 was a Monday, we need to find the day of the week on January 1, 2011.
The time period spans 4 complete years: 2007, 2008, 2009, and 2010.
To determine the total number of days, we need to check which years are leap years.
A year is a leap year if it is divisible by 4.
2007: Not divisible by 4 → 365 days
2008: Divisible by 4 → 366 days (leap year)
2009: Not divisible by 4 → 365 days
2010: Not divisible by 4 → 365 days
Total days =365+366+365+365=1461 days
To find the day of the week, we calculate 1461mod7:
1461=208×7+5
This means 1461 days =208 weeks +5 days
Starting from Monday (January 1, 2007) and adding 5 days:
Monday → Tuesday → Wednesday → Thursday → Friday → Saturday
Therefore, January 1, 2011 was a Saturday.
The answer is Option 1: Saturday.