Day Calculator
Calculate the exact number of days, weeks, months, or years between two dates, or add/subtract time from a date, with options to exclude weekends and holidays.
The Day Calculator is a powerful, dynamic tool designed to calculate the time between two dates or add/subtract duration from a start date. Unlike basic calendar engines, it includes advanced features to exclude weekends, calculate regional public holidays dynamically, and break down time intervals into multiple alternative units (months, weeks, days, hours, and seconds).
curl -X POST https://toolsamurai.com/api/v1/general-utility/day-calculator \ -H "Authorization: Bearer sk_live_•••••••••••••••" \ -H "Content-Type: application/json" \ -d '{ "mode": "between", "start_date": "2026-05-26", "end_date": "2026-12-31", "include_start_end_days": false, "operation": "add", "years": 0, "months": 0, "weeks": 0, "days": 30, "holiday_preset": "us_federal", "exclude_weekends": true, "exclude_holidays": true, "skip_weekends": true, "skip_holidays": true }'
The method behind the numbers
This calculator operates in two primary modes:
**Days Between Dates:** Enter a start and end date. The tool computes the exact mathematical difference. You can configure it to include or exclude weekends (Saturday & Sunday) and public holidays based on presets (e.g. U.S. Federal or Indian Gazetted holidays). It also provides alternative units like total seconds, minutes, hours, and weeks.
**Add/Subtract Duration:** Enter a start date and specify how many years, months, weeks, or days to shift. You can toggle options to skip weekends or holidays, meaning the additions will only advance on actual business days. This is highly useful for planning shipping times, SLA deadlines, or payment milestones.
See it in practice
Calculate the duration of the summer season in the US with holidays and weekends counted.
- mode
- between
- start_date
- 2026-05-25
- end_date
- 2026-09-07
- include_start_end_days
- true
- holiday_preset
- us_federal
- exclude_weekends
- false
- exclude_holidays
- false
Advances 45 business days while skipping weekends and U.S. Federal Holidays to find the exact delivery date.
- mode
- add_subtract
- start_date
- 2026-05-01
- operation
- add
- years
- 0
- months
- 0
- weeks
- 0
- days
- 45
- holiday_preset
- us_federal
- skip_weekends
- true
- skip_holidays
- true
Frequently asked questions
What is considered a business day or working day?
A working day is typically Monday through Friday. If you toggle 'Exclude Weekends' or 'Skip Weekends', Saturdays and Sundays are omitted from the counts or date progressions.
How does the tool calculate public holidays?
The calculator implements dynamic algorithmic rules for U.S. Federal Holidays (including fixed dates like New Year's Day and Christmas, and floating dates like Thanksgiving or Memorial Day) and Indian National Holidays (Republic Day, Independence Day, Gandhi Jayanti). You can select your holiday calendar preset to automatically detect these days.
Can I include both the start and end dates in the count?
Yes! By default, date calculators count the number of nights or transitions between days. If you check 'Include Both Start/End Dates in Count', the boundary day is included, adding exactly 1 day to the final count.
How are floating holidays like Thanksgiving calculated?
We use standard calendar algorithms to locate specific days of the week in a given month. For instance, Thanksgiving is defined as the fourth Thursday in November, and Memorial Day is the last Monday in May. The calculator computes these dynamically for any year.
Put Day Calculator on your site
Free, no signup required. Customise theme, pre-fill values, or lock inputs so visitors can only change what you choose.
<iframe src="https://toolsamurai.com/embed/general-utility/day-calculator"
width="100%" height="640" frameborder="0"
style="border:0;display:block"
title="Day Calculator — ToolSamurai"></iframe>