Deadline Calculator

When this calculator helps

A deadline is rarely a date you already know — it is usually a number of days bolted onto a start date, and that arithmetic is where mistakes creep in. Use this calculator whenever you have a starting point and a duration: a project that must ship 90 days after sign-off, a 30-day notice period on a tenancy or job, a supplier invoice due 28 days after issue, or a statutory time limit such as the 14-day right to cancel a consumer purchase. You set the start date and the amount to add, and it returns the exact deadline along with the day of the week it falls on.

It is built for the practical questions that come up in UK work and admin: when does my contract notice actually run out, what date is 'within 21 days', and if a delivery is promised in six weeks, which Friday does that land on. Because you can also subtract, it doubles as a reverse planner — start from a fixed deadline and work backwards to find the date you need to begin.

How to read your result

The result is a single calendar date plus the weekday, and the weekday is often the part that matters most. A deadline that lands on a Saturday or a Sunday is no use if the office, court, or bank is closed, so always glance at the day of the week before you commit to it. This tool counts every day of the week equally — it does not skip weekends.

Be clear in your own mind whether your deadline is meant to be in calendar days or working days. 'Within 30 days' almost always means calendar days, weekends included. 'Within 14 working days' means business days only, which on a UK calendar is a noticeably longer stretch once Saturdays, Sundays and bank holidays are stripped out. This calculator handles calendar days; for working-day counts use the Working Days Calculator instead.

A worked example

Suppose you hand in your notice on a job on 04/06/2026 with a one-month notice period. Adding one month gives 04/07/2026 — a Saturday. In practice your last working day would usually be the Friday before, 03/07/2026, so the weekday flag immediately tells you something the bare date does not. If instead your tenancy required 30 calendar days' notice from the same start, you would add 30 days and land on 04/07/2026 as well, though for a longer month the two methods diverge.

Common mistakes to avoid

Most deadline errors are not arithmetic slips — they come from counting the wrong kind of day or from the wrong starting point.

• Treating 'working days' as calendar days, or vice versa — the gap between '14 days' and '14 working days' can be most of a week.
• Forgetting that a deadline can fall on a weekend or bank holiday, when the office that needs to receive your document is shut.
• Counting from the wrong day — some contracts count from the day of an event, others from the day after, so read the wording before you set the start date.
• Assuming a deadline rolls forward automatically; this tool gives the pure calendar date, so any 'next working day' shift is yours to apply.

UK bank holidays and deadlines

The big regional wrinkle in the UK is bank holidays, and they are not the same across the country. England and Wales, Scotland, and Northern Ireland each have their own list — Scotland has 2nd January and St Andrew's Day, Northern Ireland adds St Patrick's Day and the Battle of the Boyne, and some English bank holidays do not apply north of the border. So a 'within 10 working days' deadline can genuinely resolve to a different date in Glasgow than in London.

This calculator works in pure calendar days and does not skip bank holidays, which is exactly right when your deadline is specified in calendar days. But where wording says 'working days' or a process rolls a due date to the 'next working day', you need to check the relevant bank-holiday list for the nation involved and shift the result by hand. For legally binding deadlines — court service rules under the CPR, for example — defer to the official rule or a solicitor rather than to a calendar count.