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Formulas Calendars Video Lecture - CSAT Preparation - UPSC
FAQs on Formulas: Calendars
| 1. How do I find what day of the week a date falls on using calendar formulas? |  |
Ans. Use Zeller's congruence or the day-of-week formula to calculate the day without a calendar. The formula uses the date, month, and year to determine whether it's Monday, Tuesday, or another weekday. For UPSC CSAT, memorising the modulo arithmetic method helps solve calendar problems quickly without trial-and-error, saving crucial exam time during reasoning sections.
| 2. What's the trick to solving leap year problems in calendar questions? | |
Ans. A leap year occurs every 4 years, except for century years divisible by 400. So 2000 is a leap year, but 1900 isn't. Calendar formula problems often hinge on correctly identifying leap years because they affect the total number of days and how date shifts occur across years. Recognising this pattern prevents calculation errors in UPSC reasoning questions.
| 3. Why do dates shift by one day each year even though both have 365 days? | |
Ans. A regular year contains 365 days, which equals 52 weeks plus 1 extra day. This remainder shifts any given date forward by one weekday annually. Calendar formulas account for this drift, which is why March 15, 2023 (Wednesday) becomes March 15, 2024 (Thursday). Understanding remainder logic is essential for predicting future calendar patterns in competitive exams.
| 4. How do I calculate the number of odd days between two dates for calendar problems? | |
Ans. Odd days are the remainder when total days are divided by 7-they determine how many days ahead the calendar shifts. Count the total days between two dates, divide by 7, and keep the remainder. This remainder tells you how the same date will fall on a different weekday in another year. Mastering odd-day calculation is fundamental to solving calendar formula questions efficiently.
| 5. What formulas should I memorise for the calendar chapter in UPSC CSAT preparation? | |
Ans. Key formulas include Zeller's congruence for day-of-week, odd-day calculation for year shifts, and leap-year identification rules. Additionally, the concept of "calendar repetition"-when years have identical calendar layouts-appears frequently. EduRev offers detailed notes, mind maps, and flashcards on calendar formulas that break down each method with worked examples and practice problems for exam readiness.
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Apr 19, 2026 Last updated
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Video Description: Formulas: Calendars for UPSC 2026 is part of CSAT Preparation preparation. The notes and questions for Formulas: Calendars have been prepared according to the UPSC exam syllabus. Information about Formulas: Calendars covers all important topics for UPSC 2026 Exam. Find important definitions, questions, notes, meanings, examples, exercises and tests below for Formulas: Calendars.
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Video: Formulas: Calendars of CSAT Preparation have been curated by the UPSC experts, helping you revise the topic quickly for exam preparation. Watch on EduRev.
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