According to the Gregorian calendar, on which day of the week did 1 October 1994 fall?

Introduction / Context:
Day of week questions often focus on the first day of a month because that day determines the pattern for the entire month. In this problem we must find the weekday of 1 October 1994. Solving this requires using a reliable day of week method or careful counting from a known reference date while applying leap year rules correctly.

Given Data / Assumptions:
- Target date = 1 October 1994. - Calendar = Gregorian calendar. - Year 1994 is not divisible by 4 and hence is a normal year. - We seek only the weekday name corresponding to this date.

Concept / Approach:
There are two commonly used approaches for such problems. One is to choose a known reference date with a known weekday near 1994 and count the number of days between the reference and 1 October 1994, then convert the total into a remainder modulo 7. The other is to use a day of week formula that takes the day, a specific month code, year part, and century code and directly outputs the weekday through modular arithmetic.

Step-by-Step Solution:
Step 1: Using a standard algorithm, compute the day of the week for 1 January 1994. This is known to be Saturday. Step 2: Count days from 1 January to 1 October 1994 in order to see how many days have passed. This includes all days in January through September. Step 3: Month lengths in 1994 are: January 31, February 28, March 31, April 30, May 31, June 30, July 31, August 31, and September 30. Step 4: Sum these: 31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30 = 273 days from 1 January up to 30 September inclusive. Step 5: Therefore, 1 October is 273 days after 1 January, meaning 273 days have elapsed. Step 6: Compute 273 mod 7. Since 7 times 39 equals 273, the remainder is 0. Step 7: A remainder of 0 means that 1 October falls on the same weekday as 1 January. Step 8: Since 1 January 1994 is Saturday, 1 October 1994 is also Saturday.

Verification / Alternative check:
Applying a day of week formula such as Zellers type congruence for 1 October 1994 gives a numeric code that maps to Saturday. This formula integrates the day, month, adjusted year, and century into a single expression and then uses modulo 7 to determine the weekday. The resulting day confirms the counting method and matches standard calendar references for 1994.

Why Other Options Are Wrong:
- Sunday, Friday, Wednesday, and Monday represent shifts of one or more days relative to Saturday. These would require non zero remainders (1, 6, 4, 2, and so on) when dividing 273 days by 7. - Because the exact number of days from 1 January to 1 October is a multiple of 7, the weekday must remain unchanged, ruling out all alternative weekdays.

Common Pitfalls:
Mistakes often arise from miscounting month lengths, especially February and the 30 day months, or from forgetting that 273 days represent 39 exact weeks. Some students also confuse whether they should include the starting date in the count, which can shift the weekday by one. Carefully confirming month lengths and always converting the total day count into a remainder modulo 7 avoids these errors.

Final Answer:
The day of the week on 1 October 1994 was Saturday.