Calendar
In short
A calendar is a system used to organise days by naming periods like weeks, months, and years. It can also refer to a physical record or a list of planned events.
In plain words
It helps people keep track of time and know which day it is. People use them to plan meetings, remember birthdays, and mark important holidays.
A simple example
A wall calendar shows the days of the month so you can see when next Tuesday falls. A digital calendar on a phone helps you schedule a doctor's appointment.
Why it matters
Without a calendar, it would be very difficult to coordinate activities with other people. It provides a shared way to track history and plan for the future.
Easy to mix up
Do not confuse a calendar with a clock, which measures the passing hours and minutes rather than days and months.