A lunar year has 354 days, or 50 weeks and 4 days – 11 days shorter than a solar year. Learn how lunar calendars work. Read the full guide now!

Christmas 2026 is 9 weeks and 3 days from October 20. Get the full week-by-week countdown, key US holiday dates, and planning tips. Read the full guide now!

Some US retail fiscal years run 53 weeks instead of 52 under the 4-5-4 calendar. Learn how the extra week is added and why it matters. Read the full guide now!

Pregnancy is counted as 40 weeks from the last menstrual period. Learn the 280-day math, trimester weeks, and how due dates are set. Read the full guide now!

No: only February in a common year has exactly 4 weeks. See how each month breaks down into weeks and days, with a full table. Read the full guide now!

A financial year holds 52 weeks plus 1 or 2 days, but retailers use a 52-53 week calendar. See how each type works with real examples. Read the full guide now!

Count the days between two dates, divide by 7, and you have your weeks. Follow the steps with real examples and handle leap years. Read the full guide now!

100 days equals 14 weeks and 2 days. Learn the simple conversion method, see it on a real calendar, and convert any day count. Read the full guide now!

Each season lasts about 13 weeks. See exact weeks for spring, summer, fall and winter, plus astronomical vs meteorological seasons. Read the full guide now!

A decade holds 521 full weeks plus 5 or 6 extra days. See the leap-year math, the simple formula, and worked examples. Read the full guide now!