Epoch Calendar & Date Picker
Pick a date and time — or paste a Unix timestamp — and read it back in every common format, with the day of the year, ISO week, epoch day and a day-number calendar for the whole year. Everything runs locally in your browser.
Day-number calendar
The small number under each date is its day of the year (1–365, or 366 in a leap year). Wk is the ISO week number. Click a day to select it.
What is an epoch calendar?
An epoch calendar shows every date together with a number that counts from a fixed starting point. The two numbers people look for most are:
- Day of the year (also called the day number, or loosely the "Julian date"): 1 January is day 1 and 31 December is day 365, or 366 in a leap year. Factories, warehouses and the military use it for batch codes and shipping schedules.
- Unix epoch time: the number of seconds (or milliseconds) since 1 January 1970, 00:00:00 UTC. Computers store dates this way.
This page shows both. Pick any date to see its Unix timestamp, day of year, ISO week and epoch day, or browse the day-number calendar above to read the day numbers of a whole year at a glance.
Day numbers, epoch days and ISO weeks
| Number | What it counts | Example: 1 October 2026 |
|---|---|---|
| Day of year | Days since 1 January of the same year, starting at 1 | 274 (of 365) |
| Epoch day | Days since 1 January 1970 (day 0) | 20727 |
| Unix seconds | Seconds since 1970-01-01 00:00:00 UTC | 1790812800 (at 00:00 UTC) |
| ISO week | Week of the year; weeks start on Monday | 2026-W40 |
| Quarter | Three-month block of the year | Q4 |
The ISO week (ISO 8601) starts on Monday, and week 1 is the week that contains the year's first Thursday. So the first days of January can belong to the last week of the previous year. For example, 2026-W01 runs from Monday 29 December 2025 to Sunday 4 January 2026. A year has 52 or 53 ISO weeks; 2026 has 53.
The epoch day is what Java's LocalDate.toEpochDay() returns and what many databases use to store a plain date. Multiply it by 86,400 to get the Unix time of midnight UTC on that date.
Frequently asked questions
How do I find the day of the year for a date?
Pick the date above and read "Day of year" in Calendar info, or find it in the day-number calendar: the small number under each date is its day of the year. To count it yourself, add the days of all earlier months to the day of the month, and add 1 after February in a leap year.
What is day 100 of 2026?
Day 100 of 2026 is Friday, 10 April 2026. In a leap year, such as 2028, day 100 is one day earlier: 9 April.
How many days and weeks are in 2026?
2026 has 365 days, because it is not a leap year. It has 53 ISO weeks, because 1 January 2026 is a Thursday. The next leap year is 2028, with 366 days.
What is the difference between a Julian date and the day of the year?
In everyday use (manufacturing, food labels, the military), "Julian date" usually means the day of the year, often written as YYDDD, so 1 October 2026 is 26274. Astronomers use "Julian Day Number" for something else: days since 4713 BC. This page shows the everyday day-of-year number.
What is an epoch day?
An epoch day is the number of whole days since 1 January 1970. 1 January 1970 is epoch day 0, and 1 January 2026 is epoch day 20454. It is a simple way to store a date without a time or a time zone.
Can I paste a Unix timestamp in seconds?
Yes. Paste it in the timestamp box and press Load. A value with up to 11 digits is read as seconds and a longer one as milliseconds, so both 1767225600 and 1767225600000 open 1 January 2026.
Can I paste an ISO 8601 date such as 20260605T184712Z?
Yes. The same box reads ISO 8601 dates in the long form (2026-06-05T18:47:12Z) and the compact form without dashes and colons (20260605T184712Z), in upper or lower case. Z means UTC, so the page converts the time to your time zone. A date with an offset such as +08:00 is converted too, and a date with no zone is read as your local time.
Does this tool use my time zone?
Yes. Dates and times are shown in your device's time zone, and "ISO 8601 (UTC)" shows the same moment in UTC. To convert a timestamp in another time zone, use the Unix Timestamp Converter.