Calendar reasoning – If the day after tomorrow is Sunday, what day was tomorrow’s day before yesterday?

Introduction / Context:
This item stacks relative references: “day after tomorrow,” “tomorrow,” and “day before yesterday.” The reliable way to solve such problems is to set today to T, translate each phrase into an offset, and then simplify algebraically on the 7-day cycle.

Given Data / Assumptions:

• Day after tomorrow = T + 2 = Sunday (given).
• Therefore, T = Friday.
• Tomorrow = T + 1 = Saturday.
• “Tomorrow’s day before yesterday” = (T + 1) − 2 = T − 1.

Concept / Approach:
Once T is found, compute T − 1 directly. Using offsets prevents double-counting or direction errors.

Step-by-Step Solution:

Verification / Alternative check:
Compute T − 1 explicitly: Friday − 1 = Thursday. Same result.

Why Other Options Are Wrong:

• Friday/Monday/Tuesday: These correspond to T, T + 2, or T + 4 style offsets, not to T − 1.
• None of these: There is an exact correct option (Thursday).

Common Pitfalls:
Applying “day before yesterday” to the wrong anchor (e.g., to T instead of “tomorrow”). Translate the multi-part phrase literally: first move to “tomorrow,” then move two days back.

Final Answer:
Thursday