📅 Date Calculator — Add Days, Date Diff & Age

Add or subtract days from any date, calculate the difference between two dates, and compute age from a birthdate. Three calculators in one free online date tool.

Start Date

Days

Operation

How to Use

Choose a calculator tab

Select Add/Subtract to offset a date, Date Difference to find the gap between two dates, or Age to compute exact age from a birthdate.

Enter your dates

Use the native date picker or type in YYYY-MM-DD format. All calculations update instantly as you change the inputs.

Read the result

Results show in multiple units simultaneously — days, weeks, months, and years — so you can use whichever suits your needs.

Frequently Asked Questions

How do I calculate days between two dates? +

Switch to the Date Difference tab, enter a start and end date, and the result shows instantly in days, weeks, months, and years.

Can I add business days instead of calendar days? +

The current version uses calendar days. A business-days option (skipping weekends and holidays) is planned for a future update.

How accurate is the age calculator? +

Very accurate — it accounts for leap years and calculates your exact age in years, months, and days as of today.

What date range does it support? +

Any date from the year 0001 to 9999. The native browser date picker handles input validation.

Guía: Calculadora de Fechas

¿Qué es?

Tres calculadoras en una: suma o resta días a cualquier fecha, calcula la diferencia exacta entre dos fechas (días/semanas/meses/años), y calcula la edad a partir de una fecha de nacimiento. Maneja automáticamente años bisiestos y variaciones mensuales.

Cómo usar

Selecciona la pestaña: Añadir días, Diferencia, o Edad.
Ingresa la(s) fecha(s).
El resultado aparece instantáneamente en múltiples formatos.

Consejos

Para plazos de proyecto, considera días laborables en lugar de días calendario.
La diferencia en meses es útil para suscripciones y contratos.
En código, usa date-fns o Day.js en lugar de cálculos manuales con Date de JS.