Days Until Winter Calculator

Enter Calculation

Count from date

Winter (Northern Hemisphere) begins at the December solstice, approximately December 21.

Formula

Results

Days Until Winter

178

days remaining

Winter begins (December solstice)	December 21, 2026
Hemisphere	Northern

What this calculator does

The Days Until Winter Calculator tells you exactly how many days remain until the start of astronomical winter in the Northern Hemisphere, which begins at the December solstice — on or around December 21 each year. Enter any starting date and the tool counts forward to the next occurring solstice.

Note: this calculator uses the Northern Hemisphere definition of winter. In the Southern Hemisphere, December marks the start of summer instead.

Winter in the Northern Hemisphere begins at the December solstice, around December 21.

How to use it

Pick the date you want to count from (it defaults to today) and submit. The result shows the number of whole days remaining and the exact date winter begins. If December 21 has already passed in your chosen year, the calculator automatically rolls over to next year's solstice so you always get a positive countdown.

The formula explained

The calculation is a simple date difference. Both dates are normalized to midnight, converted to milliseconds, subtracted, and divided by the number of milliseconds in a day (86,400,000). The result is rounded to the nearest whole day:

$$\text{daysUntil} = \left\lfloor \frac{\text{solstice} - \text{fromDate}}{86{,}400{,}000} \right\rceil$$

We fix the solstice at December 21 as a practical approximation; the true astronomical solstice varies between December 20 and 22 depending on the year and time zone.

Worked example

Suppose today is December 1, 2024. Winter begins December 21, 2024. The difference is 20 days, so the calculator returns 20 days remaining. If instead you entered December 25, 2024 — after the solstice — it would count to December 21, 2025, giving 361 days.

The countdown is simply the number of days between today and December 21.

FAQ

When does winter officially start? Astronomical winter in the Northern Hemisphere starts at the December solstice, usually December 21 (sometimes the 20th or 22nd).

Why does my count jump to next year? Once December 21 has passed for the current year, the next winter is in the following year, so the countdown targets that date.

Is this meteorological or astronomical winter? This tool uses astronomical winter (the solstice). Meteorological winter begins December 1.