Due Date Calculator

Find the last day of an invoice, contract, court or tax deadline by adding days, weeks, months or years to a start date. If the last day is a weekend or public holiday, the first working day after it is shown under the statute you choose.

Last updated: 28 Oct 2026

Due date (last day)Tuesday 01.12.202601.11.2026 + 30 days

Period ends onTuesday 01.12.2026
ShiftNone: the last day is a working day
Start to due date30 days
Legal basisCode of Obligations Arts. 92–93: the period starts the next day; a last day that is a holiday moves to the first day that is not (unless agreed otherwise).

Public holidays: 2429 s. Ulusal Bayram ve Genel Tatiller Hakkında Kanun md. 1–2 (RG 19.03.1981/17284; 6752 s. K. ile değişik); tarihler: Diyanet İşleri Başkanlığı resmî tatil listeleri 2025 (vakithesaplama.diyanet.gov.tr/icerik.php?icerik=157), 2026 (icerik=158), 2027 (icerik=159), 2028 (icerik=193), 2029 (icerik=194); dinî bayram günleri Diyanet dinî günler listeleri 2028 (icerik=185) ve 2029 (icerik=186) ile karşılaştırıldı 23 Oct 2026 being checked against the source

How it is calculated

Contract law (Code of Obligations Arts. 92–93), civil procedure (Arts. 92–93) and tax (Tax Procedure Law Art. 18) share the rule: the period starts the next day, holidays inside it count, and only a last day that is a holiday moves the end to the next working day. Code of Obligations Art. 93 extends a period whose last day falls on “a day that the laws treat as a holiday”. Law 2429 Art. 3/A says “the weekly rest day is Sunday. This rest, of no less than 35 hours, begins on Saturday at 13:00 at the latest”; it makes the whole of Saturday a holiday only in the case of Art. 2: “when the National Day and the public holidays set out in this Law end on Friday evening, the whole of the following Saturday is a holiday”. Beyond that the tool also treats Saturday as a holiday and moves the date; that is this tool’s assumption, not a rule written in the law, so when the last day is a Saturday it is safer to act on the Friday. For eves and 28 October the Law says “from 13:00” (Arts. 1 and 2/B); the statutes say nothing about how a half day affects a period, and the tool does not move the date for them. Parties may agree otherwise in a contract (Art. 93/2). Administrative leave for public employees is not an official holiday and does not extend legal deadlines.

FormulaLast day = Start + Term; Due date = the first non-holiday from the last day onIn days: the start day is not counted and day N is the last day. In weeks: the same weekday in the last week. In months and years: the same day number in the last month, or that month’s last day if it lacks one. Holidays: Sunday, the official holidays of Law 2429 and, as this tool’s assumption, Saturday (see below); half days such as eves and 28 October do not move the date.

Add the period to the start date (in days, weeks or months).
If the day reached is a weekend or official holiday, move to the next day.
The first day that is not a holiday is the due date, the last day of the period.

Example

A 30-day invoice dated 28 September 2026 runs to Wednesday 28 October 2026; Law 2429 makes only the time from 13:00 that day part of the holiday, so the tool does not move it and shows 28 October. A 60-day term would end on Friday 27 November 2026.

Frequently asked questions

What if the due date is a holiday?

The debt automatically moves to the first working day after the holiday (Code of Obligations Art. 93). Court and tax deadlines likewise end at closing time on the first working day after it (Civil Procedure Code Art. 93, Tax Procedure Law Art. 18).

When does a one-month period from 31 January end?

February has no 31st, so on its last day: 28 February, or 29 in a leap year. If that day is a holiday, the period extends to the first working day.

Is the start day counted?

No. The day the contract is made, the invoice issued or the notice served is left out: a 10-day period from 1 March ends on 11 March.

Source

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