Example 1
- Mode: days between dates
- 2026-01-01
- 2026-01-31
30
How many days are there from January 1, 2026, to January 31, 2026? The result is 30 full days.
Date Calculator
The calculator counts the days between two dates, or adds and subtracts days, weeks, months, and years. From January 1, 2026, to January 31, the result is 30 days. 90 days after January 1, 2026, is Wednesday, April 1, 2026.
Result
Enter a start date and an end date. The result will appear here.
If you only need the number of days between two dates, use difference between dates. To add only a number of days, use add days to a date. For a time of day, use time duration.
How it works
Start1 Jan 2026
End31 Jan 2026
Days30
In “Days between dates” the calculator counts whole days from midnight on the start date to midnight on the end date. It uses UTC, so the time zone on your computer does not change the number of days. January 1 to January 2 is one day, so January 1 to January 31, 2026, is 30 days, not 31. That is 4 weeks and 2 days. January 1, 2026, falls on a Thursday, and January 31, 2026, falls on a Saturday.
In “Add or subtract” the calculator first adds or subtracts years and months on the calendar. It then adds weeks and days, counting each day from midnight to midnight. 90 days after January 1, 2026, is Wednesday, April 1, 2026. An empty field means zero.
When the target month does not have that day, the result falls on the last day of that month. One month after January 31, 2026, is Saturday, February 28, 2026. One month after January 31, 2024, is Thursday, February 29, 2024.
Any number you enter has to be a whole number. A minus sign moves the date backward: 90 days before April 1, 2026, is Thursday, January 1, 2026.
When the end date is earlier than the start date, swap the two dates. In this mode the result does not go below zero.
The calculator uses the date only, not the time of day. Clock times are on the time duration page, and working days are on a separate page.
Formula
days = (end − start) / 86,400 seconds
date = years and months on the calendar, then weeks × 7 and days
Both formulas count from midnight UTC. From January 1 to January 31 there are 30 days. One month after January 31, 2026, is February 28, 2026.
How to use
- Leave the mode on “Days between dates”. In Start date, enter January 1, 2026. In End date, enter January 31, 2026. The result is 30 days, and the end date falls on Saturday.
- Switch to “Add or subtract”. In Start date, enter January 1, 2026. In Days, enter 90. Leave Years, Months, and Weeks empty. The result is Wednesday, April 1, 2026.
- In “Add or subtract”, enter February 28, 2024, in Start date. Enter 1 in Days. Leave Years, Months, and Weeks empty. The result is Thursday, February 29, 2024.
- In “Add or subtract”, enter April 1, 2026, in Start date. Enter −90 in Days. Leave Years, Months, and Weeks empty. The result is Thursday, January 1, 2026.
- In “Add or subtract”, enter January 31, 2026, in Start date. Enter 1 in Months. Leave Years, Weeks, and Days empty. The result is Saturday, February 28, 2026.
Days between two dates
From midnight on January 1 to midnight on January 31, 30 days pass. 90 days after January 1, 2026, is Wednesday, April 1, 2026.
- days
- A full day runs from midnight to midnight. From Thursday, January 1, 2026, to Saturday, January 31, 2026, there are 30 days, which is 4 weeks and 2 days.
- adding
- The calculator adds years and months on the calendar, then adds weeks and days from midnight to midnight. 90 days after January 1, 2026, is Wednesday, April 1, 2026.
- month
- One month after January 31, 2026, is Saturday, February 28, 2026. In 2024, one month after January 31 is Thursday, February 29, because February has 29 days.
Examples
Example 2
- Mode: add or subtract
- 2026-01-01
- 90 days
2026-04-01
What date is 90 days after January 1, 2026? Wednesday, April 1, 2026.
Example 3
- Mode: add or subtract
- 2024-02-28
- 1 day
2024-02-29
What date is the day after February 28, 2024? Thursday, February 29, 2024, because 2024 is a leap year.
Example 4
- Mode: add or subtract
- 2026-01-31
- 1 month
2026-02-28
What date is one month after January 31, 2026? Saturday, February 28, 2026, because February has 28 days that year.
Related calculators
Frequently asked questions
How many days are there from January 1 to January 31, 2026?
From midnight on January 1, 2026, to midnight on January 31, 2026, there are 30 days, which is 4 weeks and 2 days. January 1, 2026, falls on a Thursday, and January 31, 2026, falls on a Saturday.
What date is 90 days after January 1, 2026?
Wednesday, April 1, 2026.
What date is one month after January 31, 2026?
Saturday, February 28, 2026. February 2026 has 28 days, so the result falls on the last day of the month.
What date is the day after February 28, 2024?
Thursday, February 29, 2024. In a common year, the day after February 28 is March 1.
Does this include a time of day?
No. The calculator uses the date only. Clock times are on the time duration page.
Does this skip weekends and holidays?
No. The calculator counts every calendar day, including weekends and holidays. Working days are on a separate page.
Can I subtract days, months, and years?
Yes. A minus sign in days, weeks, months, or years moves the date backward. 90 days before April 1, 2026, is Thursday, January 1, 2026.
What if the end date is earlier than the start date?
Swap the start date and the end date. In this mode the result does not go below zero.
How is this different from Difference between dates?
Here you can count the days between two dates, or add and subtract days, weeks, months, and years. Difference between dates only counts the days.
Sources
A civil day, meaning one calendar day, has 86,400 seconds and starts at midnight UTC.
Page updated September 30, 2026.