Specifying only the hour or minute isn't permitted. The first day of the year (January 1) is a Wednesday and the year is a leap yearĪ time string can specify a time with precision to the minute, second, or to the millisecond.The first day of the calendar year (January 1) is a Thursday or.Therefore, Decemoccurs during the week 1953-W01. For example, the first Thursday of 1953 was on January 1, so that week-beginning on Monday, December 29-is considered the first week of the year. The first week of the year is the week that contains the first Thursday of the year. That means it's possible for the first few days of January to be considered part of the previous week-year, and for the last few days of December to be considered part of the following week-year. Each week begins on Monday and ends on Sunday. The week of the year is a two-digit string between 01 and 53. A valid week string consists of a valid year number, followed by a hyphen character (' -', or U+002D), then the capital letter ' W' (U+0057), followed by a two-digit week of the year value. Months of the yearĪ week string specifies a week within a particular year. While month 02, February, normally has 28 days, it has 29 days in leap years. Scientists occasionally add leap seconds to the calendar (seriously) to handle the remaining three ten-thousandths of a day and to compensate for the gradual, naturally occurring slowing of Earth's rotation. The adjustments to the algorithm (taking a leap year when the year can be divided by 400, and skipping leap years when the year is divisible by 100) help to bring the average even closer to the correct number of days (365.2425 days). Adding a day to the year every four years essentially makes the average year 365.25 days long, which is close to correct. Leap years help to adjust the calendar to keep it synchronized with the actual position of the planet in its orbit. Although the calendar year is normally 365 days long, it actually takes the planet Earth approximately 365.2422 days to complete a single orbit around the sun. Leap yearsĪ leap year is any year which is divisible by 400 or the year is divisible by 4 but not by 100.

(1 B.C.) or earlier.Ī year is normally 365 days long, except during leap years. are not supported, so HTML doesn't support years 1 B.C.E. Make sure any older dates account for this.įor the purposes of HTML dates, years are always at least four digits long years prior to the year 1000 are padded with leading zeroes (' 0'), so the year 72 is written as 0072. While the Gregorian calendar wasn't created until the year 1582 (replacing the similar Julian calendar), for HTML's purposes, the Gregorian calendar is extended back to the year 1 C.E.

While user interfaces may allow entry of dates using other calendars, the underlying value always uses the Gregorian calendar. In order to simplify the basic format used for date strings in HTML, the specification requires that all years be given using the modern (or proleptic) Gregorian calendar.

Utc time plus or minus minutes