Calendar – General Aptitude for GATE, PSU, ESE, AE/JE | Priyanka Ma’am

Calendar is an important topic in General Aptitude and is frequently asked in GATE, PSU, ESE, AE/JE exams. It tests your logical ability to calculate days, dates, and years.

Basic Concepts

Calendar questions are based on calculating the day of the week for a given date.

• Odd Days: Number of extra days beyond complete weeks
• 1 week = 7 days

Types of Years

• Ordinary Year: 365 days → 1 odd day
• Leap Year: 366 days → 2 odd days

Leap Year Conditions:

• Divisible by 4
• Not divisible by 100 (unless divisible by 400)

Important Concepts

1. Odd Days Calculation

Total days ÷ 7 → Remainder = Odd Days

2. Month Codes (Non-Leap Year)

• Jan – 0
• Feb – 3
• Mar – 3
• Apr – 6
• May – 1
• Jun – 4
• Jul – 6
• Aug – 2
• Sep – 5
• Oct – 0
• Nov – 3
• Dec – 5

3. Century Codes

• 1600 → 6
• 1700 → 4
• 1800 → 2
• 1900 → 0
• 2000 → 6

Solved Examples

Example 1

Find the day on 1 Jan 2020.

2020 is leap year. Known: 1 Jan 2020 = Wednesday

Example 2

How many odd days in 100 years?

100 years = 76 ordinary + 24 leap
Odd days = 76×1 + 24×2 = 76 + 48 = 124 → 124 mod 7 = 5 odd days

Example 3

Find day after 50 days from Monday.

50 mod 7 = 1 → Tuesday

Example 4 (GATE Level)

What was the day on 15 August 1947?

Known historical fact → Friday

Shortcut Tricks

• Memorize month codes
• Use odd day method
• Remember reference dates (like 1 Jan 2000 = Saturday)
• Convert large years into cycles of 400 years

Previous Year Concept Type Questions

Q1. What day is 100 days after Sunday?

100 mod 7 = 2 → Tuesday

Q2. How many leap years in 200 years?

= 200/4 − 200/100 + 200/400 = 50 − 2 + 0 = 48

Exam Tips

• Focus on odd days concept
• Practice date-based questions
• Memorize important codes
• Avoid lengthy calculations

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