For purposes of calendar repetition, the complete calendar for the year 2018 (same days and dates arrangement) will be exactly the same for which of the following later years?

Difficulty: Medium

Correct Answer: 2029

Explanation:


Introduction:
Calendar repetition questions ask in which future year the same arrangement of days and dates will reappear. For example, 1 January must fall on the same weekday, and the year type (leap year or non-leap year) must also match. Here we need the year whose calendar is identical to that of 2018.


Given Data / Assumptions:
Base year = 2018. 2018 is a non-leap year (since it is not divisible by 4). We want the next future year with: (a) Same year type (non-leap). (b) Same weekday for 1 January, and hence the same pattern for all dates.


Concept / Approach:
Each non-leap year advances the starting weekday of the next year by 1 day (since 365 ≡ 1 mod 7). Each leap year advances it by 2 days (since 366 ≡ 2 mod 7). To find when the calendar repeats, we track the cumulative shift in weekdays from 2018 onward and look for a non-leap year where the total shift is a multiple of 7 days, so that 1 January falls on the same weekday again.


Step-by-Step Solution:
Step 1: Identify leap and non-leap years after 2018. 2019: non-leap, shift +1 day. 2020: leap, shift +2 days. 2021: non-leap, shift +1 day. 2022: non-leap, shift +1 day. 2023: non-leap, shift +1 day. 2024: leap, shift +2 days. 2025, 2026, 2027, 2028, etc. continue similarly. Step 2: Track cumulative shift until it is a multiple of 7 and the year is non-leap. From 2018 to 2029, the cumulative shift adds up to 14 days, which is exactly 2 full weeks (14 ≡ 0 mod 7). Also, 2029 is a non-leap year. Therefore, 2018 and 2029 have identical calendars.


Verification / Alternative check:
Instead of tracking every year manually, one can remember that non-leap year calendars usually repeat every 11, 6, and 11 years (in a 28-year cycle), depending on positions of leap years. Starting from 2018, adding 11 gives 2029, which fits the pattern and is non-leap, confirming the result.


Why Other Options Are Wrong:
2023: Weekday pattern does not match 2018 exactly. 2027: Also does not align with both the first weekday and leap/non-leap structure. 2022: The weekday of 1 January differs from that in 2018. 2034: Occurs later in the repetition cycle and does not give the earliest match.


Common Pitfalls:
Learners often assume that calendars repeat every 11 years automatically, forgetting that leap years disturb this simple repetition. Always check both the total weekday shift and the leap-year status of the target year.


Final Answer:
The calendar for the year 2018 repeats in 2029.

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