1 Month Notice Period Calculator

A month is a date on the calendar, not 30 days

One month's notice ends on the same numbered day of the next month. Notice on March 15 ends April 15. Notice on January 31 ends February 28 in 2026, because February has 28 days and there is no 31st to land on. The length of the period moves with the calendar: 28, 29, 30 or 31 days.

Thirty days is a different promise. From January 31, thirty days lands on March 2, three days after the calendar month reading. From March 15, thirty days lands on April 14, one day before the calendar reading. Neither is wrong. They answer different questions, and the gap only matters when someone is counting the days to a payroll cut or a start date somewhere else.

Four weeks is the third reading, and it is the shortest of the three for most dates. March 15 plus 28 days is April 12, a Sunday. An employee who assumed the 15th of April would be off by three days, which is long enough to strand a handover.

Count from the day you hand it in

The day you serve notice is normally day zero, and the count starts the next morning. Notice served on March 15, a Sunday in 2026, runs through April 15 for a calendar month, which is 31 days on the clock. Notice served on March 1 under the same reading ends April 1, also 31 days.

Some contracts use an older reading, where a month that starts on the 1st ends on the last day of that same month. March 1 to March 31, 30 days, is the same month, not the same date of the next one. The panel has that as a separate mode, labeled "day before the same date", because the two readings differ by a day or more and payroll departments do notice.

Whichever reading your contract uses, write the last day into the resignation email and get the date confirmed in writing. A date that lives only in a conversation can move; a date in a reply cannot.

Four readings, and how far apart they land

The panel shows all four readings at once, because the spread between them is the whole risk. For a notice served on January 31, 2026, the readings run from 27 days to 30 days. For a notice served on June 30 or August 31, the calendar and 30 day readings agree exactly, and only the four week reading is short.

Read the table as a warning about month ends. The 29th, 30th and 31st are the days where readings drift apart the most, because the next month may not have that date. If your start date at a new job is fixed, work backward from it and put the reading in writing.

What US law asks for

US federal law does not set a notice period for an individual who quits. Most private employment is at will, which means either side can end the relationship at any time, with or without notice, unless a contract, a union agreement or a state rule says otherwise. A one month notice period in the US is a contract term or a company policy, not a statute.

The large federal rule runs the other way. The WARN Act requires employers with 100 or more workers to give 60 calendar days of written notice before a plant closing or a mass layoff, under the Department of Labor's WARN guidance. Sixty days is twice a month, and it covers layoffs, not resignations. Some states run their own mini WARN laws with different thresholds, so a large layoff can carry two sets of notice rules.

For an individual resignation, the practical answer is the offer letter, the employee handbook and the employment agreement. Those documents set the notice period, and the calculator above counts the dates once you know which reading applies.

What UK law asks for

In the UK the floor is statutory. Section 86 of the Employment Rights Act 1996 sets the minimum notice: an employee with one month or more of service must give at least one week, an employer must give one week for service under two years, one week for each year of service from two to twelve years, and twelve weeks at twelve years or more. A contract can require more than the minimum, and one month is a common contractual term on both sides.

The gov.uk notice periods page states the same ladder for redundancy situations and adds the key sentence: an employer may give more than the statutory minimum, but not less.

So a UK employee with, say, four years of service is owed four weeks of notice from the employer, while the employee owes one week unless the contract says a month. A "1 month notice period" in a UK contract is a contractual term sitting on top of that floor, and the calendar month reading above is the one UK tribunals generally use for it.

Weekdays, weekends and the last working day

Notice periods are counted in calendar days, so weekends sit inside the period and still count toward its length. The weekdays are the days someone is likely to be at work. Notice from January 31 to February 28, 2026 covers 28 calendar days and 20 weekdays. Notice from March 15 to April 15 covers 31 calendar days and 23 weekdays. Notice from December 31 to January 31, 2027 covers 31 calendar days but only 21 weekdays.

When the last day lands on a Saturday or Sunday, the practical last working day is either the Friday before or the Monday after, and the contract decides which. The panel prints both. February 28, 2026 is a Saturday, so the two candidates are February 27 and March 2. Hand over keys, badges and laptop on your final working day, not on the calendar date.

Public holidays are not removed from the weekday count, because they differ by state and by employer. If your period contains a holiday, subtract it yourself from the weekday figure and confirm the last working day with HR.

Dates that break the pattern

Month ends are the usual trouble. January 31 plus one month has no 31st to land on in February, so the same date reading clamps to the 28th in 2026 and the 29th in 2028. The clamp matters in both directions: a notice served on January 31, 2028 runs 29 days, one day longer than the same notice in 2026.

December 31 plus one month lands on January 31 of the next year, and in 2027 that date is a Sunday, so the last working day is January 29 or February 1. A notice served on the 30th of June lands on July 30, which works, but the same notice served on the 31st of August has no August 31 pair to worry about in September, so it clamps to the 30th.

The day before reading has its own quirk at month ends. From January 31 it gives February 27, only 27 days. That is why contracts spell out a month end rule instead of relying on arithmetic, and why the panel shows all four readings instead of picking one for you.

Putting the date in writing

Write the notice with three dates in it: the date you are serving it, the last day you expect to work, and the reading you used, in words. "One calendar month from March 15, 2026, ending April 15, 2026" leaves less room for argument than "one month's notice". Ask for a written confirmation of the last day and the final pay date.

Check the period against the pay cycle before you send it. If pay runs from the 25th to the 24th, a notice ending on the 15th splits a pay period, and some employers pay the stub weeks apart. Benefits usually run to the end of the month the employment ends in, but plan cover is different, so ask.

Keep the email thread and the reply. If the start date at the next job moves, or the employer wants a different last day, the written record is what settles which side owes what. This page does date arithmetic; it is not legal advice, and a contract clause beats any calculator.