Time zones and daylight saving: how to get them right
UTC, offsets, daylight saving and timestamps: what you need to schedule meetings and calculate dates without mistakes.
Add or subtract days from a date
Find a future or past date by days, weeks or months.
Runs in your browser
Counts every day on the calendar.
Result
Saturday, 31 January 2026
ISO 8601: 2026-01-31
The resulting date falls on a weekend.
What it does: Add or subtract days from a date
Find the date a number of days, weeks, months or years from now — or how long ago. You can also count only Monday-to-Friday weekdays, for example for delivery deadlines.
It works with calendar days, not 24-hour blocks, so daylight-saving changes never shift the result by a day.
How to use it
- Pick the start date.
- Choose add or subtract and the amount.
- Choose the unit: calendar days, weekdays, weeks, months or years.
- Read the resulting date and its day of the week.
Examples
30-day payment terms
An invoice issued on 1 January 2026 with 30-day terms is due on 31 January 2026.
End of month
31 January + 1 month = 28 February (29 in a leap year), because 31 February doesn't exist.
Limits, formulas and assumptions
- Weekdays: it steps day by day skipping Saturdays and Sundays; holidays aren't deducted.
- Months and years: the day of the month is kept and, if it doesn't exist, the last day of the target month is used.
- Legal or administrative deadlines may have their own rules (business days, holidays); check them case by case.
Frequently asked questions
Does the start date count?
No: adding 1 day to today gives tomorrow. Weekdays are counted starting from the next day.
What if I start on a Saturday and add 1 weekday?
You get the following Monday.
Does subtracting a month and adding it back give the original date?
Not always: 31 March − 1 month = 28 February, and 28 February + 1 month = 28 March.
Related guides
Related tools
Date difference calculatorDays, weeks and months between two dates, with weekdays. World clockCurrent time in several time zones and a converter. Unix timestamp converterConvert timestamps in seconds or milliseconds to dates. HEX and RGB color pickerPick a color and convert between HEX, RGB and HSL. Color palette generatorHarmonious palettes with accessible contrast checks. Digital storage converterConvert bytes, KB, MB, GB and their binary equivalents.