EZ Calculators

Date Calculator

This date calculator adds or subtracts days, weeks, months or years from any date you pick. Enter a start date and an amount, or combine several units at once, and you'll get the result date with its weekday, week number and day of the year.

Calculation and content reviewed by EZ Calculators Editorial Team on .

Enter values

Move forward or backward from a valid civil date with one calendar unit or a combined interval. The workspace keeps month-end behavior, ordered calculation stages, elapsed days, weekdays, and ISO week-year context visible.

Build the scenario below, then calculate for a complete result report.

Runs in your browser
Calendar unitsYears and months stay calendar-aware
Month boundariesChoose the end-of-month convention
Elapsed daysDST-safe date ordinals

Choose the direction and starting date

Add moves forward on the calendar; subtract moves backward. The start date is validated as a real Gregorian date before any interval is applied.

Step 1
Enter a real Gregorian calendar date from year 0001 through 9999.

Build the calendar interval

Use a single amount for a quick lookup, or combine years, months, weeks, and days in one ordered calculation.

Step 2
Enter a nonnegative whole number.
Calendar arithmetic, not a deadline ruling

Courts, agencies, contracts, and workplaces can use special rules for trigger days, inclusive endpoints, weekends, holidays, filing times, and time zones. Confirm the governing rule before acting on a consequential deadline.

What date is 90 days from today?

Add the days one calendar date at a time, weekends included. From Monday, October 5, 2026, 90 days later is Sunday, January 3, 2027. Thirty days later is Wednesday, November 4, 2026. Enter today's date, choose Add, type the number of days, and the calculator returns the date and its weekday.

How to use the date calculator

Pick Add to go forward or Subtract to go back. Then choose Single unit for one amount, like 45 days, or Combined interval for something like 1 month, 2 weeks and 3 days.

For a "from today" question, enter today's date as the start date. The calculator counts calendar days, so weekends and holidays are included.

  1. Choose Add or Subtract.
  2. Enter the start date.
  3. Pick Single unit or Combined interval.
  4. Type the amount and choose days, weeks, months or years.
  5. If months or years are involved, pick a month-end rule.
  6. Calculate and read the result date, weekday and calendar details.

Days, weeks and months from today

Here are common lookups from a start date of Monday, October 5, 2026. Swap in your own start date and the calculator does the same counting.

Results from Monday, October 5, 2026
IntervalResult dateWeekday
30 days from todayNovember 4, 2026Wednesday
90 days from todayJanuary 3, 2027Sunday
100 days from todayJanuary 13, 2027Wednesday
12 weeks from todayDecember 28, 2026Monday
6 months from todayApril 5, 2027Monday
45 days agoAugust 21, 2026Friday
90 days agoJuly 7, 2026Tuesday

How to add days to a date

Adding days moves one calendar date per day. July 7, 2026 plus 30 days is August 6, 2026. Weeks are just seven days each, so 12 weeks is the same as 84 days.

Months and years work differently. They move to the same day number in the target month, which is why 6 months from October 5 is April 5 no matter how many days fall in between. The 90-day lookup above covers 2 months and 29 days of calendar, not 3 months.

Formula guide
  • Result date = start date + (7 x weeks + days)
  • Month stage = start date moved by (12 x years + months) calendar months
  • Combined result = month stage + (7 x weeks + days)

How to subtract days from a date

Choose Subtract and the calculator walks backward through the calendar with the same rules. October 5, 2026 minus 45 days is Friday, August 21, 2026. Minus 90 days is Tuesday, July 7, 2026.

Subtracting is handy for working back from a due date. If something is due on a set day and you need to start 8 weeks earlier, subtract 8 weeks from the due date.

Month-end dates and combined intervals

"One month after January 31" has no clean answer, because February has no 31st. The default rule moves to the last valid day, so January 31, 2026 plus one month is February 28.

The preserve month-end rule keeps a month-end start on the last day of the target month. February 28, 2026 plus one month is March 28 by default and March 31 with preserve month-end on.

In combined mode, years and months go first, then weeks and days. January 31, 2026 plus 1 month, 2 weeks and 3 days lands on February 28 first, then 17 days later on March 17, 2026.

Weekday, week number and day of year

Each result shows its weekday, the ISO week (for example 2026-W53), the day of the year, the quarter and whether the year is a leap year. It also splits the days you moved into weekdays and weekend days.

ISO weeks can belong to a neighboring year near New Year. January 3, 2027 is in ISO week 2026-W53, which is why the year is shown with the week number.

When a deadline follows its own counting rule

Courts, agencies, contracts and employers often say whether the first day counts, whether the last day can fall on a weekend, and which holidays push a deadline. Federal Rule of Appellate Procedure 26 is one example.

This tool counts plain calendar days and doesn't know any holiday list. For working days only, use the business days calculator. For an official deadline, check the rule that governs it.

Sources

These references cover the date format, the leap-year rule and an example of formal deadline counting.

ISO: date and time format (ISO 8601)Explains the year-month-day format and ISO week dates.U.S. Naval Observatory: leap yearsThe Gregorian rule for which years have February 29.U.S. Naval Observatory: calendarsBackground on the civil calendar used for date math.Federal Rule of Appellate Procedure 26A real deadline rule covering trigger days, weekends and holidays.

FAQ

What is 30 days from today?

Add 30 calendar days to today's date, weekends included. From Monday, October 5, 2026, that's Wednesday, November 4, 2026. Enter your own start date to get the answer for any day.

How many weeks from today is a date 12 weeks out?

Twelve weeks is 84 days. From Monday, October 5, 2026, 12 weeks later is Monday, December 28, 2026. Adding whole weeks always lands on the same weekday you started on.

Is one month from a date the same as 30 days?

No. A month moves to the same day number in the next month, which can be 28 to 31 days later. Thirty days is always exactly 30 calendar dates. The two answers often differ.

What is one month after January 31?

With the default rule it's the last day of February: February 28 in 2026, or February 29 in a leap year. Other systems may use their own month-end rule.

Does the date calculator skip weekends and holidays?

No. It counts every calendar day. It does show how many weekdays and weekend days you crossed, but for working days only, use the business days calculator.

Can I add years, months, weeks and days together?

Yes. Choose Combined interval and fill in any mix of the four. Years and months are applied first, then weeks and days, and a stage table shows each step.

What date range does it support?

Start and result dates must fall between the years 0001 and 9999 on the Gregorian calendar. It works with dates only, not times of day or time zones.