Date and Days — Your Complete Date Calculation Resource
Find the day of the week for any date, count days between dates, check ISO week numbers, calculate business days, and explore all our free date tools — all built for Australia.
📅 Day of Week Finder
Quick Answer: What Are Dates and Days?
A date is a specific point in the Gregorian calendar identified by day, month, and year (e.g. 20 February 2026). A day is either a 24-hour period or one of the seven days of the week (Monday through Sunday). Date and day calculations — counting days between dates, finding day of the week, calculating business days — are fundamental to scheduling, legal timekeeping, financial planning, and everyday life. Australia uses the DD/MM/YYYY date format; the international standard is YYYY-MM-DD (ISO 8601).
All Date and Day Calculators
Days Between Dates
Count calendar days between any two dates
Business Days Calculator
Count Mon–Fri working days
Date Calculator
Add or subtract days from any date
Days Until
Countdown to any future date
Age in Days
Find your exact age in days
Week Number Calculator
ISO week number for any date
Date Difference Tool
Years, months, and days breakdown
Holiday Calendar
Australian public holidays 2026
Time Period Calculator
Measure any date interval
Count Days Online
Free online day counter
Weekends Between Dates
Count Saturdays and Sundays
Leap Year Calculator
Check if any year is a leap year
Calendar Calculator
Advanced date and calendar maths
How Many Days Between
Step-by-step day counting guide
Understanding the Gregorian Calendar
All date calculations on DateAndDays.com.au use the Gregorian calendar, the internationally adopted civil calendar introduced by Pope Gregory XIII in October 1582 as a refinement of the Julian calendar. It was adopted throughout the British Empire — and subsequently in Australia — in September 1752.
Key facts about the Gregorian calendar
- A common year has 365 days divided into 12 months
- A leap year has 366 days (an extra day added to February)
- The average year length is 365.2425 days
- Leap years occur in years divisible by 4, except century years not divisible by 400
- Weeks run Monday to Sunday under ISO 8601 (Sunday to Saturday in some US conventions)
- The calendar cycles through all possible day/date combinations every 400 years (146,097 days)
Month lengths
| Month | Days | Month | Days |
|---|---|---|---|
| January | 31 | July | 31 |
| February | 28 / 29* | August | 31 |
| March | 31 | September | 30 |
| April | 30 | October | 31 |
| May | 31 | November | 30 |
| June | 30 | December | 31 |
* February has 29 days in leap years (years divisible by 4, except century years not divisible by 400).
Australian Date Format and Standards
Australia uses the DD/MM/YYYY date format in everyday communication — for example, 20/02/2026 for 20 February 2026. This follows the day-month-year order used throughout most of the world, inherited from British conventions.
For technical and international contexts, the ISO 8601 standard (YYYY-MM-DD, e.g. 2026-02-20) is recommended to avoid ambiguity — particularly important when communicating with the United States, which uses MM/DD/YYYY.
Common date format confusion
- 04/05/2026 in Australia = 4 May 2026
- 04/05/2026 in the USA = 5 April 2026
- 2026-04-05 in ISO 8601 = 5 April 2026 (unambiguous)
All calculators on DateAndDays.com.au accept dates in ISO 8601 format (YYYY-MM-DD) via the date picker, ensuring accuracy regardless of locale settings.
Start Calculating — Pick Your Tool
All our date calculators are free, accurate, and work entirely in your browser. No sign-up required.
Days Between Dates →Authoritative External References
- ISO 8601 — International Date and Time Standard — International Organization for Standardization
- Gregorian Calendar — History and Structure — Encyclopaedia Britannica
- Daylight Saving Time Standards — National Institute of Standards and Technology (NIST)
- Acts Interpretation Act 1901 — Date and Time Definitions — Australian Government
- Calendar Systems Reference — TimeAndDate.com
Frequently Asked Questions
What day of the week was I born?
Enter your birth date in the Day of Week Finder above and click "Find Day". For example, 20 February 2026 is a Friday.
What are dates and days?
A date is a specific point in the calendar (e.g. 20 February 2026). A day is a 24-hour period or the name of a day of the week. Date calculations help measure, plan, and schedule time.
Why does Australia use DD/MM/YYYY?
Australia inherited the day-month-year format from British convention. ISO 8601 (YYYY-MM-DD) is recommended for international or technical use to avoid ambiguity with the US MM/DD/YYYY format.
How many days are in each month?
Jan: 31 · Feb: 28/29 · Mar: 31 · Apr: 30 · May: 31 · Jun: 30 · Jul: 31 · Aug: 31 · Sep: 30 · Oct: 31 · Nov: 30 · Dec: 31. Mnemonic: knuckles = 31-day months; valleys = shorter months.
How many days are in a year?
365 in a standard year, 366 in a leap year. The Gregorian calendar averages 365.2425 days per year. 2026 is not a leap year.
What time zones does Australia use?
AEST (UTC+10) for NSW, VIC, QLD, TAS, ACT; ACST (UTC+9:30) for SA and NT; AWST (UTC+8) for WA. Daylight saving is observed in NSW, VIC, SA, TAS, and ACT.