Tax Deadline Calculator
Count down to important dates and events with this tax deadline calculator. Never miss a deadline or celebration.
How It Works
Select your target date to see:
- Days remaining
- Weeks and months until the event
- A visual countdown timer
- Percentage of time elapsed
Practical Applications
- Event planning and preparation
- Project deadlines and milestones
- Holiday and vacation planning
- Personal goal tracking
Measuring the Gap Between Two Dates
Two dates can be "one day apart" in several different senses, and the one you want depends on the question:
| Measure | 2026-03-01 to 2026-03-02 |
|---|---|
| Calendar days between | 1 |
| Days inclusive of both ends | 2 |
| 24-hour periods elapsed | 1, or 0.958 across a spring DST change |
| Business days | 1, unless one is a weekend |
``javascript
// Calendar days, DST-safe: compare at UTC midnight
const daysBetween = (a, b) => {
const utc = (d) => Date.UTC(d.getFullYear(), d.getMonth(), d.getDate());
return Math.round((utc(b) - utc(a)) / 86400000);
};
`
Normalising to UTC midnight before subtracting removes both the DST problem and any
time-of-day component, which is almost always what "days between" is meant to mean.
When US Tax Returns Are Due
15 April, moved to the next business day when it falls on a weekend or a DC holiday.
| Year | Date |
|---|---|
| 2026 | Wed, April 15, 2026 |
| 2027 | Thu, April 15, 2027 |
| 2028 | Mon, April 17, 2028 |
| 2029 | Mon, April 16, 2029 |
| 2030 | Mon, April 15, 2030 |
The deadline shifts for two reasons: weekends, and Emancipation Day — a District of Columbia
holiday on 16 April that legally affects federal filing deadlines nationwide.| Other deadlines | Date |
|---|---|
| Q1 estimated payment | 15 April |
| Q2 estimated payment | 15 June |
| Q3 estimated payment | 15 September |
| Q4 estimated payment | 15 January (following year) |
| Extension deadline (Form 4868) | 15 October |
| S-corp and partnership returns | 15 March |
An extension extends the time to file, not the time to pay. Tax owed is still due in
April, and interest accrues from that date regardless of the extension.The Traps in Date Arithmetic
Months are not 30 days. Adding one month to 31 January has no correct answer, and every
library picks differently — 28 February, 2 March or an error. Decide which your business
needs before the edge case decides for you.
Days are not always 86,400 seconds. Daylight saving makes one day 23 hours and another
25. Adding n * 86400000 milliseconds drifts by an hour twice a year, which is enough to
move a date across midnight and return an answer one day out.
`javascript
// Correct — the Date object normalises overflow and handles DST
const addDays = (date, days) => {
const result = new Date(date);
result.setDate(result.getDate() + days);
return result;
};
// Correct — calendar days, unaffected by DST or time of day
const daysBetween = (a, b) => {
const utc = (d) => Date.UTC(d.getFullYear(), d.getMonth(), d.getDate());
return Math.round((utc(b) - utc(a)) / 86400000);
};
`
Months are zero-indexed in JavaScript. new Date(2026, 0, 1) is January. new
Date(2026, 12, 1) is January 2027, silently.
Parsing is not portable. new Date("2026-08-30") is parsed as UTC, while
new Date("2026/08/30")` is parsed as local — the same calendar date, a day apart in some
zones. Always parse ISO 8601, and construct with explicit components when the time matters.
Time Zones Decide the Answer
| Question | Depends on |
|---|---|
| How many days until an event? | The viewer's zone |
| Is this subscription expired? | UTC, always |
| What day of the week was this? | The zone the event happened in |
| When does "tomorrow" start? | The viewer's zone |
Reference Points
| Interval | Days |
|---|---|
| Week | 7 |
| Month (average Gregorian) | 30.44 |
| Quarter | 91.31 |
| Year | 365.2425 |
| Leap year | 366 |