Phần hướng dẫn bên dưới chưa có bằng tiếng Việt nên được hiển thị bằng tiếng Anh. Bản thân máy tính đã được dịch đầy đủ.
Cách sử dụng máy tính này
- Pick or type a date.
- The weekday and calendar details appear instantly.
Công thức
The weekday follows from counting days since a known reference date modulo 7. Week numbers follow ISO 8601: weeks start on Monday, and week 1 is the week containing the year's first Thursday. A year is a leap year if it is divisible by 4, except centuries not divisible by 400.
Leap year: (y mod 4 = 0 and y mod 100 ≠ 0) or y mod 400 = 0
ISO week 1 contains 4 January
Examples
- 1 January 2000 was a Saturday.
- 4 July 1776 was a Thursday.
- 2100 is not a leap year; 2000 was.
Câu hỏi thường gặp
Why does the ISO week year sometimes differ from the calendar year?
Dates in the first days of January can belong to the last ISO week of the previous year, and late-December dates can belong to week 1 of the next year.
Does it work for historical dates?
It uses the Gregorian calendar for all dates (the proleptic Gregorian calendar). Countries switched from the Julian calendar at different times, from 1582 onwards, so very old dates may differ from historical records.
What is the day of the year?
Its position in the year: 1 January is day 1 and 31 December is day 365 (366 in leap years).