Reference · 25 terms
Definitions for week-numbering, calendar, and fiscal-year terms used across the site.
1 term
The Australian financial year runs 1 July to 30 June. The ATO uses it for income tax, company tax, and Business Activity Statement cycles.
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A BAS quarter is one of four quarterly periods used by the ATO for Business Activity Statement reporting under the Australian financial year.
The Broadcast Calendar is a Monday-start standard used by US broadcasters and ad-buying systems to align inventory, billing, and audience reporting.
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A calendar week is the standard 7-day cycle used to measure weeks. The first and last day depend on the numbering standard in force.
A calendar year is the 12-month period from 1 January to 31 December. It runs 365 days, or 366 days in a leap year.
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Financial year is the Commonwealth-English term for fiscal year. Australia uses 1 July to 30 June; the UK splits individual and corporate years.
The first-Thursday rule defines ISO week 1 as the week containing the first Thursday of the year — equivalently, the week containing 4 January.
A fiscal year is a 12-month accounting and tax reporting period distinct from the calendar year. Start dates vary by country and jurisdiction.
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The Gregorian calendar is the solar calendar introduced in 1582 by Pope Gregory XIII. It is the international civil standard for dates today.
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ISO 8601 is the internationally agreed standard for date and time representation. Week 1 is the first week of the year containing at least four days of the new year.
An ISO week date identifies a date by its week-based year, week number, and weekday number in the format YYYY-Www-D — for example, 2026-W22-4.
ISO weeks suit operational cadence and sprints. Months suit financial reporting and accruals. The two rarely align cleanly.
ISO weekday numbering assigns 1 to Monday and 7 to Sunday. Other systems use different conventions, so conversion matters.
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A Julian Day is a continuous count of days since noon UT on 1 January 4713 BCE. Astronomers and software use it for date arithmetic.
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An ordinal date is an ISO 8601 format that identifies a day by its day-of-year number. The format is YYYY-DDD.
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A payroll week is a pay-period unit used by payroll systems to align cycles to weekly, fortnightly, or 4-weekly schedules across jurisdictions.
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A quarter is a 3-month period within a fiscal or calendar year. Quarter numbering depends on whether the year starts in January or July.
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The Retail 4-5-4 Calendar is an NRF standard that splits each quarter into 4+5+4 weeks, giving retailers 13-week quarters for comparable reporting.
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US week numbering is a Sunday-start convention where Week 1 contains 1 January. It powers US payroll, retail, and Excel's default WEEKNUM.
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Week 53 is the 53rd ISO week, occurring in years where 1 January or 31 December falls on a Thursday — roughly every 5–6 years.
Week Commencing, written WC or w/c, identifies a calendar week by its Monday start date — for example, WC 25 May 2026 covers Mon 25 May to Sun 31 May.
Week Ending, written WE or w/e, identifies a week by its closing date — for example, WE Sat 30 May 2026 names the Sunday-start week that closes on that Saturday.
Week of year is the ordinal position of a week within a year. The value depends on the numbering standard — ISO, US, or Australian Financial Year.
The week-based year is the year component of an ISO week date. It differs from the calendar year for dates near 1 January or 31 December.
A working week is the subset of a calendar week treated as business days — typically Monday to Friday, with regional variations in the Middle East and Israel.