01 Key Concepts
Days in a Week
There are 7 days in a week, so days repeat in a cycle of 7.
Odd Days
The number of days left over after dividing total days by 7 — used to find what day of the week a date falls on.
Leap Year Rule
A year is a leap year if divisible by 4, except century years (ending in 00), which must be divisible by 400.
Days in Each Month
30 days: April, June, September, November. 31 days: the rest, except February (28, or 29 in a leap year).
Ordinary vs. Leap Year Odd Days
An ordinary year has 1 odd day (365 = 52 weeks + 1 day). A leap year has 2 odd days (366 = 52 weeks + 2 days).
03 Key Formulas
- Odd days = Total days mod 7
04 Solved Examples
Example 1 Is the year 2024 a leap year?
- Check divisibility by 4: 2024 ÷ 4 = 506, no remainder.
- 2024 is not a century year, so no further check is needed.
Answer: Yes, 2024 is a leap year
Example 2 Is the year 1900 a leap year?
- 1900 is divisible by 4, but it is a century year.
- Century years must be divisible by 400. 1900 ÷ 400 is not a whole number.
Answer: No, 1900 is not a leap year
Example 3 If January 1 is a Monday, what day is January 15?
- From Jan 1 to Jan 15 is 14 days later.
- 14 ÷ 7 = 2 remainder 0, so 14 days is exactly 2 full weeks.
- The day of the week repeats.
Answer: Monday
05 Practice Questions
1Is 2028 a leap year?
Yes (divisible by 4, not a century year)
2Is 2000 a leap year?
Yes (divisible by 400)
3How many odd days does an ordinary year have?
1
4How many days does February have in a leap year?
29
5If today is Wednesday, what day is it in 7 days?
Wednesday
📄 Time & Calendar — Downloadable Worksheet
10 questions with a full answer key. Grab the PDF to print, or try the interactive version in your browser.