How to use the date converter
Step 1 — Enter a date, or pick one
Type it, paste it, or tap the calendar icon inside the field to choose one visually — the picker shows date and time, and Set, or pressing Enter, drops the choice into the field. Put each date on its own line to convert several at once. The parser accepts ISO dates, slash and dot dates, written dates in either order, full ISO timestamps with an offset, Unix timestamps, Excel serial numbers, and the words today, tomorrow, yesterday and now.
Step 2 — Resolve the 01/02/2026 problem
A slash date is genuinely ambiguous: 01/02/2026 is 1 February to most of the world and 2 January in the United States. The Reading 01/02/2026 as control decides which, so the tool never guesses. Where the day is above 12 the reading is unambiguous and an obvious mistake corrects itself.
Step 3 — Choose calendars and time zones
Leave both calendars on Gregorian for ordinary dates. Set the input calendar to Hijri, Saka or Persian and the tool reads your input in that system; set the output calendar to add a converted card. Both time zone fields search all 419 IANA zones by city, country or abbreviation — a date with a time is a different instant in every zone, so this can move the date by a day.
Step 4 — Read the grouped results
Results are colour-coded so you can find what you need at a glance: standard date formats in blue, time formats in purple, machine and spreadsheet values in amber, other calendars in green, your custom pattern in teal. Every card copies individually, and the whole set copies or exports as CSV. Underneath, the Day Details tiles give weekday, weekend status, day of year, ISO week, quarter, days in month with business days, leap year, distance from today and the exact UTC offset used.
Adding or subtracting from a date
The Add or subtract tab shifts a date by days, business days, weeks, months, years or hours. Month and year steps are calendar-accurate: 31 January plus one month gives 28 February, not 3 March — and 29 February in a leap year. Business days skip Saturdays and Sundays.
Counting days between two dates
The Days between dates tab reports the exact number of days plus a calendar breakdown in years, months and days, the count in weeks, the number of business days, and the span in hours, minutes and seconds. Either box accepts a date or a plain keyword such as today.
About the date converter
This tool takes a date in almost any written form and returns it in every format you are likely to need — ISO 8601, day-first and month-first slash dates, long and short written forms, RFC 1123, Unix timestamps, Excel serial numbers and Julian Day Numbers — plus the same date expressed in thirteen calendar systems and any time zone.
Date formats are one of the few genuinely universal sources of confusion in computing and paperwork. The same eight characters mean different days depending on who wrote them, spreadsheets store dates as numbers nobody can read at a glance, and databases hand back epoch values. This tool exists to move between all of those without guesswork.
Two design decisions matter. Impossible dates are rejected rather than silently rolled over — 31 February returns an error instead of quietly becoming 3 March, which is what a plain date object does. And calendar conversions are real: every non-Gregorian date is computed from the ICU calendar data in your browser, converting day, month and year, not just adding an offset to the year number.
Who this is for
- Developers moving between ISO strings, epoch values and human dates while debugging.
- Spreadsheet users who have a five-digit serial number where a date should be.
- Anyone working across formats — reading an American date in a European office, or the reverse.
- People transcribing records dated in Hijri, Saka, Persian or Julian calendars.
The settings explained
Input calendar
The calendar the date you typed is written in. Leave it on Gregorian for ordinary dates. Set it to another system and the tool reads your input in that calendar and converts out of it — useful when transcribing a document dated in a non-Gregorian system.
Output calendar
The calendar to convert into. Adds one result card showing the full converted date, with month name and era.
Input and output time zones
A date with a time is a different instant in every zone, so converting between zones can move the date by a day. Both fields search all 419 IANA zones by city, country or abbreviation — type india, london or PST.
Reading order
Decides whether a slash date is read day-first or month-first. Only affects ambiguous input.
Custom output format
Adds one extra card in a pattern you specify. Tokens: YYYY and YY for year; MMMM, MMM, MM, M for month; dddd and ddd for weekday; DD and D for day; HH, hh, mm, ss for time; A for AM/PM. So dddd, D MMMM YYYY gives Sunday, 23 August 2026.
The calendar systems this tool converts
Gregorian
The international civil calendar, in use since 1582 and the default for input and output. A solar calendar of 365 days, or 366 in a leap year.
Julian
The calendar Gregorian replaced. Its simpler leap rule — every fourth year with no century exception — has drifted 13 days from Gregorian, and the gap widens over the centuries. This tool computes the true Julian date through Julian Day Numbers rather than assuming a fixed 13 days, so historical dates stay correct: 15 October 1582 Gregorian resolves to 5 October 1582 Julian, the very discontinuity the reform created. Still used liturgically by several Orthodox churches, which is why Orthodox Christmas falls on 7 January.
Islamic (Hijri)
A purely lunar calendar of 354 or 355 days, so it moves about 11 days earlier against Gregorian each year and its months rotate through all seasons — which is why Ramadan shifts. Two variants are offered because they can differ by a day: the Umm al-Qura calculation used officially in Saudi Arabia, and the tabular civil variant common in software.
Hebrew
A lunisolar calendar of 12 or 13 months. A leap month is inserted seven times in every nineteen years, which keeps Passover in spring instead of drifting as the Islamic months do.
Persian (Solar Hijri)
The official calendar of Iran and Afghanistan. Its year begins at the March equinox, making it one of the most astronomically accurate calendars in current use.
Indian National (Saka)
India’s official civil calendar, adopted in 1957 and used alongside Gregorian in the Gazette of India and in All India Radio broadcasts. Year 1 Saka corresponds to 78 CE, so 2026 Gregorian falls in 1948 Saka.
Buddhist, Chinese, Coptic and Ethiopic
Buddhist Era runs 543 years ahead of Gregorian and is the civil calendar of Thailand. Chinese is lunisolar with named months and a sixty-year cycle. Coptic and Ethiopic share a thirteen-month structure — twelve months of 30 days plus a short final month of five or six.
Japanese and Minguo
Japanese dates are numbered within an imperial era, so 2026 is Reiwa 8. Minguo counts from the founding of the Republic of China in 1912, making 2026 Minguo 115.
A note on Hindu Panchang dates
This tool does not output Hindu lunisolar (Panchang) dates such as tithi, nakshatra or paksha. Those depend on the moon’s position calculated for a specific place and time of day, and cannot be derived from a fixed offset applied to the year — any converter producing them from arithmetic alone is not giving you a real Panchang date. Where you need an official Indian date, use Indian National (Saka), which is India’s civil standard and is computed exactly.
Frequently asked questions
How do I convert a date to another format?
Enter it once. Every standard format is produced at the same time — ISO 8601, ISO date, DD/MM/YYYY, MM/DD/YYYY, long and short written forms, 12- and 24-hour times, RFC 1123, Unix timestamps in seconds and milliseconds, the Excel serial number and the Julian Day Number.
What is the ISO 8601 date format?
YYYY-MM-DD, optionally followed by T, a time and a UTC offset. Its value is that it sorts correctly as plain text and is unambiguous worldwide, which is why databases, APIs and log files use it. 2026-08-23 can only mean 23 August 2026.
What is the difference between MM/DD/YYYY and DD/MM/YYYY?
Only the order — which is exactly why the format is risky. The United States writes month first; nearly everywhere else writes day first. For any day above the 12th the two are distinguishable, but from the 1st to the 12th the same string means two different dates.
Does it reject impossible dates?
Yes. 31/02/2026 and 31/04/2026 return an error rather than silently becoming 3 March and 1 May. 29 February is accepted in 2024 and rejected in 2026, because 2026 is not a leap year.
How do I convert a Unix timestamp to a readable date?
Paste the number in. Ten digits are read as seconds, thirteen as milliseconds. For microsecond or nanosecond precision, or to convert in the other direction, the timestamp converter is the specialised tool.
What is an Excel serial date, and why does my spreadsheet show a number?
Excel stores dates as the number of days since 30 December 1899, so 23 August 2026 is 46257. A cell showing a five-digit number is a date whose formatting was lost. Paste that number here and you get the date back — the tool reads Excel serials directly.
What is a Julian Day Number?
A continuous day count used in astronomy, starting from 1 January 4713 BC. It is not the Julian calendar — it is a running total with no months or years, which makes date arithmetic across long spans trivial. Both are provided, and they are different things.
How do I calculate the number of days between two dates?
Use the Days between dates tab. You get the exact day count plus a calendar breakdown in years, months and days, the figure in weeks, and the number of business days excluding weekends.
How do I add 30 days, or 3 months, to a date?
Use Add or subtract, choose the unit and the amount. Month and year steps clamp correctly at month ends, so 31 January plus one month gives 28 February rather than overflowing into March.
What week number is this date?
The Day Details tiles show the ISO week number, the standard used in Europe and by most business systems. ISO weeks start on Monday, and week 1 is the week containing the first Thursday of the year — so early January can fall in week 52 or 53 of the previous year.
Can I convert several dates at once?
Yes — one per line. Each gets its own result card, and the whole set exports as CSV or copies in one go.
Is the date converter free and private?
Free with no sign-up, and everything runs inside your browser. Dates you enter are never uploaded, which matters when they come from real records.
