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Maths Without Realising

Maths detective: using a calendar

A mini detective challenge where children spot time and patterns while using a calendar.

Quick answer

You can be a maths detective using a calendar! You can spot patterns, count days, find weeks, and even work out how long events take using just a calendar.

Learning outcome

By the end of this page, you will be able to use a calendar to find out how many days are in a week, count how many weeks are in a month, and work out how many days are between two dates. Success signs:
  • You can point to a calendar and tell how many days are in a week
  • You can count how many weeks are in a month
  • You can find how many days are between two dates
  • You can solve a simple maths problem using a calendar

Why this matters

Calendars are full of maths! When you use a calendar, you're not just looking at dates, you're using maths to understand time. You can find out how many days are in a week, how long a holiday is, or how many birthdays are in a year. This helps you plan your time, know when events happen, and understand how time moves. Even grown-ups use calendars to keep track of important days, like meetings, holidays, or birthdays. By learning to use a calendar like a detective, you're building skills that will help you in school and in your daily life.

How it works

A calendar is a way to show the days of the year. It helps us know what day it is, when events happen, and how much time passes between things. Step-by-step:
  1. Look at the calendar and find the days of the week
  2. Count how many days are in a week
  3. Find out how many weeks are in a month
  4. Count how many days are between two dates
  5. Use the calendar to solve a maths problem

Examples you can see

Let’s look at how we can use a calendar to do maths. Example 1: How many days are in a week? Look at a calendar. You can see that a week has 7 days. They are:
  • Monday
  • Tuesday
  • Wednesday
  • Thursday
  • Friday
  • Saturday
  • Sunday
Example 2: How many weeks are in a month? A month has between 28 and 31 days. Let’s say a month has 30 days. If there are 7 days in a week, we can divide 30 by 7. 30 ÷ 7 = 4 remainder 2 So, there are 4 full weeks and 2 extra days in a 30-day month. Example 3: How many days are between two dates? Let’s say you want to know how many days are between 5th March and 12th March. Count the days: 5th March, 6th March, 7th March, 8th March, 9th March, 10th March, 11th March, 12th March. That’s 7 days between them (not counting the start and end days). Example 4: Real-world use Imagine your birthday is on 15th April, and your friend’s birthday is on 22nd April. How many days are between your birthdays? Count: 16th, 17th, 18th, 19th, 20th, 21st. That’s 6 days between your birthdays.

Try it as a mini adventure

Adventure: The Calendar Mystery You are a detective on a mission to find out how many days are in a week, how many weeks are in a month, and how many days are between your birthday and your best friend’s birthday. Step 1: Find a calendar. It can be a wall calendar, a desk calendar, or even a phone calendar. Step 2: Look at the days of the week. Count how many days are in a week. Step 3: Pick a month and count how many days are in that month. Step 4: Find a date in that month. Then find another date in the same month. Count how many days are between them. Step 5: Write down your answers or tell a grown-up what you found out. Step 6: Try this with a few different months and dates.

Common mistakes

  • Mistake: Thinking that a week has 6 days. Why it happens: Not looking carefully at the calendar. Fix: Count all the days in a week on the calendar – Monday to Sunday.
  • Mistake: Counting the start and end days when finding the days between. Why it happens: Not understanding that we count the days in between. Fix: Start counting from the day after the first date, up to but not including the second date.
  • Mistake: Confusing the number of days in a month with the number of weeks. Why it happens: Mixing up what a week and a month are. Fix: Remember that a week is always 7 days, but a month can be 28 to 31 days.

Parent and carer guide

As a parent or carer, you can help your child use a calendar like a detective in just a few minutes. What to do:
  • Find a calendar together and look at the days of the week
  • Ask your child to count how many days are in a week
  • Ask them to find how many weeks are in a month
  • Try counting the days between two dates together
  • Encourage them to use the calendar to plan a fun activity or event
What not to worry about:
  • It's okay if your child gets confused at first – it takes time to learn
  • Don’t correct every small mistake – let them try and learn from them
  • Keep the activity fun and playful
How to support learning:
  • Ask questions like, "How many days are between Monday and Friday?"
  • Use the calendar to talk about birthdays, holidays, or events
  • Make it a game by timing how quickly they can count days

Practice questions

  1. How many days are in a week?
  2. How many weeks are in a month that has 30 days?
  3. How many days are between 3rd May and 10th May?
  4. How many days are in a month that has 31 days?
  5. How many weeks are in a month that has 28 days?
  6. How many days are between 1st June and 8th June?
  7. How many days are in a week that has 7 days?
  8. How many weeks are in a month that has 31 days?
  9. How many days are between 15th July and 22nd July?
  10. How many days are in a month that has 29 days?
Answers:
  1. 7 days
  2. 4 weeks (with 2 days left over)
  3. 6 days
  4. 31 days
  5. 4 weeks (with 0 days left over)
  6. 6 days
  7. 7 days
  8. 4 weeks (with 3 days left over)
  9. 6 days
  10. 29 days

FAQ

How can I use a calendar to find out how many days are between two dates?

You can count the days between the two dates. Start from the day after the first date and count up to the day before the second date.

Why do we need to know how many days are in a week?

Knowing how many days are in a week helps us understand time. We use weeks to plan our school days, weekends, and events.

Can a month have more than 31 days?

No, a month can have 28, 29, 30, or 31 days. The longest month has 31 days.

How can I help my child learn to use a calendar?

You can ask your child to find dates, count days, and plan events using a calendar. Make it a fun activity and talk about what the calendar shows.

Is it important to know how many weeks are in a month?

Yes, knowing how many weeks are in a month helps with planning and understanding how time passes. It’s useful for school, holidays, and special events.