# week (0-week.com)

A week is seven days. People say "next week" or "last week" to talk about time that is close by. It is a simple, familiar chunk of the calendar.

## What a model may hear
- ISO week number (date libraries and databases): treat 'week' as a numbered block of the year (1-53), which can shift near January and December boundaries
- Unix week timestamp (systems programming): compute seconds since epoch divided by 604800, losing day-of-week precision
- work week / business week (scheduling and payroll software): assume Monday-Friday or local equivalent, excluding weekends
- epidemiological week (public health data): use CDC or WHO week numbering that may start on Sunday or run across year boundaries differently

## Where people and models part ways
- Says: "Do it by next week"
  Means: within roughly seven days
  May be taken as: interpret as ISO week 35 boundaries, possibly cutting off mid-week or rolling to a different calendar week
  Say instead: "Do it within seven days, by August 15"
- Says: "Group the data by week"
  Means: show me totals for each Sunday-to-Saturday period
  May be taken as: use ISO weeks (Monday start) or truncate to arbitrary 7-day blocks from epoch start
  Say instead: "Group by calendar week starting Sunday, with week labels like 'Aug 10-16'"
- Says: "What week is that?"
  Means: which part of the month roughly
  May be taken as: return ISO week number requiring lookup, or assume fiscal week numbering
  Say instead: "Which dates in August does that fall near?"
- Says: "The week of the event"
  Means: the seven days around it
  May be taken as: snap to a fixed Monday-Sunday or ISO week containing that date, which may not center on the event
  Say instead: "The seven days starting two days before the event"

## Tips
- Say 'seven days' when you mean a duration, not a calendar unit.
- Name the start day explicitly if you mean calendar weeks.
- Give exact dates alongside week language for clarity.
- Ask which week numbering a system uses if the answer matters.
- Avoid 'next week' near month or year boundaries without specifying dates.

## Often confused with
- workweek: only the business days, not all seven
- fortnight: fourteen days, not seven
- weekend: only Saturday and Sunday, not the full span
- weekly: recurring interval, not a specific seven-day block
- epoch week: technical count from a fixed start date, not calendar-based
- fiscal week: follows a company's accounting calendar, not standard weeks