Days Until a Date
Days Since a Date (How long ago?)
Days Ago (N days)
Add/Subtract Days
Years/Months/Days Since
Tip: For “how many years since 2018”, set Start to 2018-01-01 and leave As of blank.
What this date calculator does
This date calculator helps you add or subtract days, find the number of days between two dates, and quickly check important timelines. Whether you're tracking deadlines, project schedules, events, or personal milestones, the tool gives you the total number of days instantly. It works with the standard Gregorian calendar and handles leap year logic without any extra setup.
How to use it
Choose a start date, then decide whether you want to count forward or backward. You can add or subtract days, weeks, months, or years based on what you need. If you're trying to measure the gap between two dates, select both dates and the calculator will show the exact difference in days. Days Until • Days Ago • Add/Subtract • Years Since
Working days vs total days
Some situations require only working days instead of full calendar days. If you're planning around office schedules, business deadlines, or delivery estimates, you’ll want to focus on business days. Total days include weekends and holidays, but business days only count the days people typically work.
Days between two dates
If you want to find the number of days between a start date and an end date, enter both and let the tool return the total number of days. This is helpful for trip planning, pregnancy timelines, school projects, or tracking how long something has been running.
Add or subtract days
If you need to add 1 day, 30 days, or even several months or years to a specific date, use the add/subtract option. This is useful when calculating deadlines, warranty periods, renewal dates, or future events.
Working days
If you’re calculating business turnaround time or project sprint cycles, use working days instead of full days. This gives a more realistic estimate for professional or business-related planning.
Business days, holidays and edge cases
Business-day mode excludes weekends (Sat/Sun) and can skip holidays you provide. This mode is essential for SLA, lead-time and legal window calculations. The engine also correctly handles:
- Leap years (Feb 29),
- End-of-month transitions (e.g., Jan 31 → Feb 28/29),
- Time-zone safe date-only math (the scripts use UTC-safe day arithmetic to avoid DST/offset errors).
Implementation & privacy
All calculations run client-side. Date inputs don’t leave the browser. The code uses UTC-safe date math and calendar-aware routines for Y/M/D differences. Client-side math keeps latency near-zero and protects private workflow data. If you later add server-side features, keep the client version as the default for most users.
Quick tips & copyable microcopy
-
Prefer ISO format
YYYY-MM-DDto avoid locale confusion. - Show both Y/M/D and total days on legal or audit pages to serve both readers and machines.
- For recurring deadlines, test with business-day mode and custom holiday lists.
🛠️ What this tool can do
- Add/Subtract days from a given date
- Find difference between two dates (days or Y/M/D)
- Jump to next/previous weekday
- Business days between dates (skip weekends; optional holidays)
Uses the civil calendar with real month lengths and leap years.
📋 Inputs
-
Start date: e.g.,
YYYY-MM-DD - Days to add/subtract: integer (negative to subtract)
- End date: for difference mode
- Time zone: your local time is used
⚖️ Edge cases
- Leap years (Feb 29) handled correctly
- End-of-month transitions (e.g., Jan 31 → Feb)
- No data leaves your browser (local-only)
🎯 Difference “in Y/M/D” vs “total days”
- Total days: exact day count between two dates
- Y/M/D: calendar-accurate years → months → days, not just days ÷ 365
💡 Tips
-
Prefer ISO format (
YYYY-MM-DD) to avoid locale confusion.\li> - Business days mode excludes Sat/Sun; you can add holiday dates to exclude them too.
- Time-of-day is ignored; calculations use local midnight.
🧩 How to use
- Choose a mode: Add/Subtract or Difference.
- For Add/Subtract enter a Start date and a number of days (negative to subtract), then press Calculate.
- For Difference: enter Start and End dates to see total days and Y/M/D.
- (Optional) Enable Business days to skip weekends and supply holidays.
Days Calculator – Frequently Asked Questions
Enter a start date and an end date into the calculator. The tool returns the total number of days between those dates and accounts for leap years using the Gregorian calendar.
Yes. Choose a base date and select how many days, weeks, months, or years to add or subtract. The calculator will show the resulting calendar date.
Yes. Date calculations use the Gregorian calendar and include correct leap year logic, so results remain accurate across February 29 and multi-year spans.
Total days count every calendar day between two dates. Business days count only working days (typically Monday through Friday) and exclude weekends; use the working days option for scheduling or delivery estimates.
Select the "Days Until a Date" option, choose August 13 for the desired year, and the calculator will display the number of days remaining from the current date.
Select "Days Since a Date", pick September 30 in the appropriate year, and the tool will show how many days have passed since that date.
Use the "Days Ago (N days)" option, enter 2015, and the calculator will return the exact calendar date that many days before the current date.
Open "Days Until a Date", select September 17 for the desired year, and the calculator will show the number of days remaining from the current date.