CALENDAR | CSAT | REASONING | UPSC CSE

Описание: CALENDAR | CSAT | REASONING | UPSC CSE

Stop counting days on your fingers! 📅 In this mindmap video for UPSC CSE by Dr. Sonu Patel, we decode **Calendar Problems**—a high-scoring area in the CSAT Reasoning section.

UPSC doesn't want you to be a human calendar; they want to test your understanding of remainders. We break down the ultimate cheat code of "Odd Days," decode the massive "Century Year Trap," and give you the 5-second trick to find out exactly when a calendar year will repeat itself!



📅 *Video Mindmap: Calendar Problems*

► *1. The Magic of "Odd Days" (The Foundation)*
• *What is it?* The remainder you get when you divide the total number of days by 7.
• Normal Year (365 Days): 365 / 7 = 52 weeks + **1 Odd Day**.
• Leap Year (366 Days): 366 / 7 = 52 weeks + **2 Odd Days**.

► *2. The Leap Year Trap (High Yield for UPSC)*
• *Normal Rule:* If a year is divisible by 4, it’s a Leap Year (e.g., 2024, 2028).
• *The Century Trap:* If a year ends in "00", it MUST be divisible by *400* to be a leap year.
• Example: 1600 and 2000 are leap years. But 1700, 1800, and 1900 are NOT leap years! (UPSC loves to catch students here).

► *3. Century Odd Days (Memorize 5-3-1-0)*
• 100 Years = *5* Odd Days
• 200 Years = *3* Odd Days
• 300 Years = *1* Odd Day
• 400 Years = *0* Odd Days (The cycle resets!)
• Trick Application: This is how you calculate the exact day of historical events like 15th August 1947!

► *4. Repetition of Calendars (The 5-Second Trick)*
• When will the exact same calendar (matching days and dates) be used again? Just divide the year by 4 and check the remainder!
• *Remainder 0 (Leap Year):* Add *28 Years* (e.g., 2024 will repeat in 2052).
• *Remainder 1 (Leap Year + 1):* Add *6 Years* (e.g., 2025 will repeat in 2031).
• *Remainder 2 or 3 (Leap Year + 2 or 3):* Add *11 Years* (e.g., 2026 will repeat in 2037).

Stop fearing dates and start collecting your 2.5 marks easily!

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