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Calendar Grid

Calendar Grid problems give the first day of a month (e.g., 'The 1st of the month is Monday') and ask for the weekday of another date in the same month. You must calculate the position of the date in the weekly grid, accounting for the starting day.

10Worksheets
200+Practice Questions
BeginnerDifficulty
1-2 hoursHours to Master

What You'll Learn

Introduction & Overview Why This Matters How to Solve Pro Tips & Tricks
Shortcut Methods Common Mistakes Practice Worksheets Exam Importance

Introduction to Calendar Grid

Calendar Grid problems give the first day of a month (e.g., 'The 1st of the month is Monday') and ask for the weekday of another date in the same month. You must calculate the position of the date in the weekly grid, accounting for the starting day.

Prerequisites

Knowledge of weekdays order Understanding of 'first day of month' concept Simple addition and modulo 7 Days in month (for boundary checks)
Why This Matters: Calendar Grid problems appear in 1-2 questions in SSC CGL and Banking PO exams. They test understanding of weekly cycles within a month.

How to Solve Calendar Grid Problems

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Step 1: Note the given first day of the month (e.g., 1st = Monday)

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Step 2: Identify the target date (e.g., 15th of the same month)

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Step 3: Calculate the offset: target_date - 1 (days after the 1st)

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Step 4: Add the offset to the first day's weekday index

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Step 5: Apply modulo 7 to wrap around

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Step 6: Convert the resulting index back to weekday name

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Step 7: Verify that the date exists in the month

Pro Strategy: Use the formula: (first_day_index + (date - 1)) mod 7 gives the weekday index of the date. Memorize that dates 1, 8, 15, 22, 29 fall on the same weekday (7 days apart).

Example Problem

Example: If the 1st of March is Wednesday, what day is the 15th of March? Solution: Step 1: 1st March = Wednesday (index 2 if Monday=0, Wednesday=2) Step 2: Target date = 15 Step 3: Offset = 15 - 1 = 14 days after 1st Step 4: 14 mod 7 = 0 Step 5: Wednesday + 0 = Wednesday Answer: Wednesday Example 2: If 1st is Friday, what day is 20th? Solution: Step 1: Friday index = 4 Step 2: Offset = 20 - 1 = 19 Step 3: 19 mod 7 = 5 Step 4: 4 + 5 = 9 mod 7 = 2 → Tuesday Answer: Tuesday

Pro Tips & Tricks

  • Dates with difference of 7 fall on the same weekday (1st, 8th, 15th, 22nd, 29th)
  • If 1st is Monday, then: 1=Mon, 2=Tue, 3=Wed, 4=Thu, 5=Fri, 6=Sat, 7=Sun, then repeats
  • To find weekday of date D: (weekday_of_1st + D - 1) mod 7
  • Use 0=Monday, 1=Tuesday, ..., 6=Sunday for easy calculation
  • The 15th is always same weekday as 1st if the month has 28+ days (always true)
  • For large dates, subtract 7 repeatedly until less than 8 to find the base date

Shortcut Methods to Solve Faster

Date D and date (D-7) fall on same weekday
If 1st = X, then Dth = X + (D-1) days forward
All dates with same remainder mod 7 (with 1-based indexing) share weekday
Quick formula: (first_day_index + D - 1) % 7

Common Mistakes to Avoid

Forgetting to subtract 1 from the date (1st has offset 0)
Using 1-based indexing for weekdays incorrectly
Not wrapping around Sunday to Monday
Assuming all months have 31 days when checking boundaries

Exam Importance

Calendar Grid is an important topic for various competitive exams. Here's how frequently it appears:

SSC CGL
1-2 questions
BANKING PO
1-2 questions
RAILWAYS RRB
2-3 questions
INSURANCE
1-2 questions

Ready to Master Calendar Grid?

Start with Worksheet 1 and work your way up to expert level! Each worksheet includes:

20 practice questions
Detailed solutions
Step-by-step explanations
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