WhichWeek

Always know which week it is. WhichWeek shows your ISO week number with a single glance — and counts days between any two dates.

WhichWeek is the fastest way to know your ISO week number.

Open the app and your current ISO week number is front and center — bold, clear, and impossible to miss. No digging through a calendar. No mental arithmetic. Just the week number.

WEEK VIEW • Your current ISO week number, large and legible • The exact date range for that week (Monday to Sunday) • Step forward or back through weeks and years with the stepper controls • Tap Today to jump straight back to the current week • Leap year indicator so you never lose track of the extra day

DAYS VIEW • Pick any two dates and instantly see the number of days between them • Broken down into full weeks and remaining days • Perfect for project planning, countdowns, and date arithmetic

DESIGNED WITH CARE • Pure SwiftUI — fast, native, and responsive • Supports Dynamic Type for accessibility • Full Dark Mode and Light Mode support • Works in portrait and landscape • Available on iPhone, iPad, Mac, and Apple Watch

ISO WEEK NUMBERS ISO 8601 defines week numbering used widely in business, finance, logistics, and project management across Europe and beyond. Week 1 is the week containing the first Thursday of the year. WhichWeek follows this standard precisely.

NO ADS. NO TRACKING. NO SUBSCRIPTIONS. WhichWeek is a one-time purchase. No accounts required, no data collected, no network requests made.