Date Format Converter
Convert between calendar dates, JD Edwards (CYYDDD) Julian, YYYYMMDD, and more. It runs entirely in your browser, so the file never leaves your computer.
One date, a dozen ways of writing it
Type a date into any field and every other representation fills in at once — the calendar date, the YYYYMMDD number, the day of year, ISO and US week numbers, and the JD Edwards Julian form.
That is the useful shape for this job. You rarely want one conversion; you want to see the same date in whichever notation the system in front of you expects.
The JD Edwards CYYDDD date, explained properly
JD Edwards stores dates as CYYDDD: one century digit, two year digits, three digits of day-of-year. The century digit is 0 for the 1900s and 1 for the 2000s. So 126001 is day 1 of 2026 — 1 January 2026.
Two things catch people. First, a 1900s date has a leading zero that databases and exports routinely drop, so you are handed 98129 when the value is really 098129 — 9 May 1998. This reads the five-digit form correctly.
Second, and more confusing: this is not the astronomical Julian Day Number, which is a continuous day count used in science and a completely unrelated system that shares a name. If you came here for that one, this is the wrong tool.
ISO weeks and US weeks are different numbers
ISO weeks start on Monday and follow the international standard. US weeks start on Sunday, which is what Excel does by default. For a given date these two conventions frequently disagree about which week number it is.
Both are shown, so you can hand the right one to whichever system asked. There is also a CSV export covering a whole year with every format as a column — useful when you need a lookup table rather than one answer.
Questions
Common questions
What does this tool do?
It converts a date between many formats at once — a normal calendar date, the JD Edwards 'Julian' date (CYYDDD), the YYYYMMDD number, day-of-year, week numbers, and every calendar piece. Type a date in any one field and all the others fill in.
How do I convert a date?
Type into whichever field you have — the calendar date, the JDE Julian number, YYYYMMDD, or year plus day-of-year — and everything else updates instantly. You can also click 'Use today' or pick from a calendar.
What is the JD Edwards / CYYDDD Julian date?
It's how JD Edwards software stores dates: one century digit (0 for 1900s, 1 for 2000s), two year digits, then the three-digit day of the year. So 126001 means day 1 of 2026 — January 1, 2026.
My JDE date is only 5 digits — is that a problem?
No. For 1900s dates the leading century digit is a zero that databases often drop, so a value like 98129 is read as 098129 (May 9, 1998). The tool handles the 5-digit form automatically.
Is this the same as a regular 'Julian date'?
No, and this trips people up. The JDE CYYDDD format is unrelated to the astronomical Julian Day Number (a running count of days used in science). This tool does the JDE business format; it isn't the astronomy one.
What's the difference between ISO week and US week?
They number the weeks of the year differently — ISO weeks start on Monday (the international standard), US weeks start on Sunday (what Excel uses by default). The tool shows both so you can use whichever your system expects.
How do I export a whole year of dates?
Use the CSV export at the bottom. It defaults to the entire current year, so you can export it in two clicks, or set any start and end date for a smaller range. The file has every format as columns, one row per day.
Is anything uploaded?
No. Everything runs on your own computer in the browser — nothing leaves your machine.
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