Use the Calendar Days vs Working Days What Is The Difference
A calendar day is every day on the calendar, including weekdays, weekends and bank holidays. A working day usually means a day when work or business is normally carried out, often Monday to Friday, excluding weekends and sometimes excluding bank holidays.
Calendar days count every day. Working days usually count only the days that are treated as working days for the purpose you are calculating.
This matters for deadlines, delivery times, notice periods, business tasks, invoices and holiday planning. “7 calendar days” and “7 working days” can end on very different dates.
Need to count both?
Use the date calculators to compare total calendar days with working days that exclude weekends and selected UK bank holidays.
What counts as a calendar day?
Calendar days are the simplest type of date count. Every date counts: Monday, Saturday, Sunday, Christmas Day, bank holidays and ordinary weekdays.
For example, from Monday to the following Monday is 7 calendar days if you count the time between the dates, because the weekend is included.
What counts as a working day?
Working days are more context-dependent. A common UK assumption is Monday to Friday, excluding Saturday and Sunday. Some calculations also exclude a bank holiday, but that depends on the wording of the rule, contract, policy or deadline.
For example, if something is due in 5 working days from a Monday, the result may land on the following Monday if a weekend sits in the middle. If there is a bank holiday, it may move again.
Calendar days vs working days side by side
| Question | Calendar days | Working days |
|---|---|---|
| Do weekends count? | Yes | Usually no, if the working week is Monday to Friday |
| Do bank holidays count? | Usually yes | Often no, if the rule excludes bank holidays |
| Best for | Age, countdowns, total duration, event dates | Business deadlines, work planning, notice-period estimates |
| Main risk | Forgetting whether the count is inclusive | Forgetting weekends, bank holidays or contract wording |
Worked example
Suppose a task starts on Monday 1 June and must be completed within 10 days.
The difference gets bigger if the period includes a weekend, a public holiday, or a workplace closure. For exact results, use the days between dates calculator for calendar days and the working days calculator for working-day counts.
How UK bank holidays affect working days
UK bank holidays are not identical across the whole UK. England and Wales, Scotland and Northern Ireland have different calendars, so a UK working-day calculator should ask for the region rather than assuming every date is the same everywhere.
GOV.UK also states that when a bank holiday falls on a weekend, a substitute weekday normally becomes the bank holiday, usually the following Monday.
If a deadline says “working days excluding bank holidays”, select the correct UK region and exclude the relevant bank holidays for that region.
For employment, leave and notice-period questions, the calculator can estimate dates, but the contract or written statement can matter more than the generic calendar calculation.
Inclusive vs exclusive counting
Another common confusion is whether the start date counts.
- Exclusive counting: starts counting after the start date. This is common for “days between” calculations.
- Inclusive counting: counts both the start date and the end date. This can be used for some bookings, records or internal policies.
For example, 1 January to 10 January is 9 days if you count the gap between the dates, but 10 days if you include both 1 January and 10 January.
Which one should you use?
| Use case | Usually use | Why |
|---|---|---|
| Age or birthday countdown | Calendar days | Weekends and holidays still count as real time. |
| Project deadline in business days | Working days | Non-working days may be excluded. |
| Notice period end date | Depends on wording | Contracts can use calendar days, weeks, months or working days. |
| Time until an event | Calendar time | Countdowns measure real elapsed time. |
| Timesheet or hours worked | Working time | You are counting hours worked, not dates passed. |
Why notice periods need extra care
Notice periods can be especially confusing because “one week”, “7 days”, “5 working days” and “one calendar month” do not always mean the same thing.
Acas says notice periods depend on the contract or written statement, length of service and whether someone resigns, is dismissed or is made redundant. If the contract does not say when notice starts, Acas guidance says the notice period starts the day after the employee tells the employer.
Estimating a final working date?
Use the notice-period end-date calculator, then check the result against the contract or HR guidance.
FAQs
Are weekends calendar days?
Yes. Calendar days include every day on the calendar, including Saturday and Sunday.
Are weekends working days?
Usually not if the working-day rule assumes a Monday-to-Friday working week, but some industries and contracts use different working patterns.
Do bank holidays count as working days?
Often no, but it depends on the wording of the deadline, contract or policy. UK bank holidays also vary by region.
Is 7 calendar days the same as 5 working days?
Not always. A normal Monday-to-Friday week has 5 working days and 7 calendar days, but bank holidays or different work patterns can change the result.
Should I count the start date?
It depends on the rule you are following. Date-difference calculators often exclude the start date by default, while some policies count inclusively.