Somar ou subtrair dias de uma data

Encontre a data um número de dias, semanas, meses, anos ou dias úteis antes ou depois de uma data inicial, com o dia da semana e o deslocamento em dias corridos.

Atualizado Exemplos verificados: 7

= 2026-09-29
Experimentar
Resulting date
Thursday, 29 October 2026
Resulting date: Thursday, 29 October 2026
Dia da semana
Thursday
Calendar days moved
30days

Tue 29 Sep 2026 plus 30 days is Thursday, 29 October 2026.

Tue 29 Sep 2026 plus 30 days

30 calendar days: 29 Sep 2026 to 29 Oct 202630 calendar daysStartTue 29 Sep 2026ResultThu 29 Oct 2026
Como é calculado S
  1. Add day numbers

    20725+30=2075520725 + 30 = 20755

    Day numbers count from 1 January 1970 in the proleptic Gregorian calendar.

  2. Resultado

    Thursday, 29 October 2026, 30 calendar days later.

Sobre Somar ou subtrair dias de uma data

Days and weeks are added to the start date's day number, a running count of days since 1 January 1970, so month lengths and leap years take care of themselves. Months and years move the month and keep the day of the month; when that day doesn't exist in the target month, the result is the month's last day, the same rule as Excel's EDATE. Business days are counted one at a time from the day after the start, stepping over the chosen weekend days.

Typical uses are due dates, return and cooling-off windows, visa and licence expiry dates and medication courses. 100 days after 15 January 2026 is Saturday, 25 April 2026, and 5 business days after Friday, 16 January 2026 is the following Friday.

Month steps can't always be undone: 31 March 2026 minus one month is 28 February, and 28 February plus one month is 28 March. Public holidays are not skipped here; the working-day deadline calculator takes a holiday list.

Exemplos resolvidos

31 January plus one month in a leap year

Start date
2024-01-31
Operation
Add
Amount
1
Unidade
Meses
Resulting date
2024-02-29
Dia da semana
Thursday
Calendar days moved
29 days

Fonte de verificação: Python dateutil: date(2024,1,31) + relativedelta(months=1) = 2024-02-29 (Excel EDATE agrees)

100 days after 15 Jan 2026

Start date
2026-01-15
Operation
Add
Amount
100
Unidade
Days
Resulting date
2026-04-25
Dia da semana
Saturday

Fonte de verificação: Python 3.8: date(2026,1,15) + timedelta(days=100)

Leap day plus one year

Start date
2024-02-29
Operation
Add
Amount
1
Unidade
Anos
Resulting date
2025-02-28
Calendar days moved
365 days

Fonte de verificação: Python dateutil: date(2024,2,29) + relativedelta(years=1) = 2025-02-28

31 March minus one month

Start date
2026-03-31
Operation
Subtract
Amount
1
Unidade
Meses
Resulting date
2026-02-28
Calendar days moved
-31 days

Fonte de verificação: Python dateutil: date(2026,3,31) − relativedelta(months=1) = 2026-02-28

Perguntas

How do I work out the date 90 days from today?

Enter today as the start date, choose Add, type 90 and pick Days. Counting starts on the day after the start date, so 90 days from 1 January 2026 is 1 April 2026: January, February and March hold 31 + 28 + 31 = 90 days. In a leap year the same count from 1 January ends on 31 March, because February has 29 days.

What is 31 January plus one month?

28 February, or 29 February in a leap year such as 2024. A day of the month that doesn't exist in the target month is moved back to that month's last day, which is how Excel's EDATE and Python's dateutil relativedelta behave. The same rule makes 31 March minus one month 28 February 2026, and 31 August plus one month 30 September.

How do I add business days to a date?

Count forward from the day after the start date and skip each weekend day. Friday, 16 January 2026 plus 5 business days is Friday, 23 January, 7 calendar days later; 10 business days before 15 January 2026 is 1 January. Public holidays are not skipped in this calculator, whereas Excel's WORKDAY(start, days, holidays) skips any holidays you list.

Is adding one year the same as adding 365 days?

Only when the year ahead has no 29 February in it. From 15 January 2027 one year later is 15 January 2028, 365 days on, but from 1 March 2027 one year later is 1 March 2028, 366 days on, because 29 February 2028 falls in between. 29 February 2024 plus one year becomes 28 February 2025 under the month-end rule.

Qual é a precisão de “Somar ou subtrair dias de uma data”?

A precisão depende dos dados inseridos e das hipóteses do método. O cálculo decimal usa 50 algarismos significativos, mas estimativas, métodos numéricos e dados de origem podem ter menor precisão; o arredondamento exibido não elimina essas limitações. Exemplos resolvidos verificados com fontes independentes: 7. Por exemplo, “31 January plus one month in a leap year” é verificado com Python dateutil: date(2024,1,31) + relativedelta(months=1) = 2024-02-29 (Excel EDATE agrees).

De onde vem o método?

Howard Hinnant — chrono-compatible low-level date algorithms; Microsoft Excel EDATE and WORKDAY functions (same month-end and business-day conventions).

Sobre esta calculadora

N(result)=N(start)±n(days),day=min⁡(d,days in target month)(months)N(\text{result}) = N(\text{start}) \pm n \quad (\text{days}),\qquad \text{day} = \min(d, \text{days in target month}) \quad (\text{months})

Fontes

  1. Howard Hinnant — chrono-compatible low-level date algorithms
  2. Microsoft Excel EDATE and WORKDAY functions (same month-end and business-day conventions)

Verificado com as referências

Esta calculadora inclui 7 exemplos resolvidos com respostas de fontes independentes. Eles fazem parte do conjunto de testes e você também pode executá-los aqui.

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