Due Date Countdown Calculator
Track your pregnancy journey with our due date countdown calculator. Knowing how many days remain until your expected delivery helps you prepare physically, emotionally, and practically for baby's arrival.
Pregnancy Countdown Milestones
| Weeks Until | Trimester | Milestones |
|---|---|---|
| 28+ weeks | First | Morning sickness, first ultrasound |
| 14-28 weeks | Second | Gender reveal, baby movements |
| 14-0 weeks | Third | Nursery prep, hospital bag |
| 4 weeks | Final month | Maternity leave begins |
| 2 weeks | Almost there | Final preparations |
Due Date Calculator
``javascript
function pregnancyCountdown(dueDate) {
const today = new Date();
const due = new Date(dueDate);
const diffTime = due - today;
const diffDays = Math.ceil(diffTime / (1000 * 60 * 60 * 24));
const diffWeeks = Math.floor(diffDays / 7);
// Calculate current pregnancy week (assuming 40 week pregnancy)
const currentWeek = 40 - diffWeeks;
return {
days: diffDays,
weeks: diffWeeks,
currentPregnancyWeek: Math.max(1, currentWeek),
trimester: currentWeek <= 13 ? 'First' : currentWeek <= 26 ? 'Second' : 'Third',
fullTerm: diffDays <= 21, // 37+ weeks is full term
dueDate: due.toLocaleDateString('en-US', { month: 'long', day: 'numeric', year: 'numeric' })
};
}
`
Preparing for Baby's Arrival
The countdown helps pace preparations: complete nursery by 36 weeks, pack hospital bag by 37 weeks, install car seat by 38 weeks. Remember that only 5% of babies arrive on their exact due date—most arrive within two weeks before or after.
Understanding Due Date Variability
Due dates are estimates, not guarantees. First babies often arrive late (41+ weeks), while subsequent pregnancies may come earlier. Use the countdown as a guide while remaining flexible. "Full term" begins at 37 weeks; most doctors won't induce before 39 weeks unless medically necessary.
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 |