Struct Julian 

pub struct Julian;

The Julian Calendar.

The Julian calendar is a solar calendar that was introduced in the Roman Republic under Julius Caesar in 45 BCE, and used in Europe and much of the western world until it was eventually replaced by the more accurate Gregorian calendar.

This implementation extends proleptically for dates before the calendar’s creation.

While no country uses the Julian calendar as its civil calendar today, it is still used by eastern Christian churches to determine lithurgical dates like Christmas and Easter.

Era codes

This calendar uses two era codes: bce (alias bc), and ce (alias ad), corresponding to the BCE and CE eras.

Months and days

The 12 months are called January (M01, 31 days), February (M02, 28 days), March (M03, 31 days), April (M04, 30 days), May (M05, 31 days), June (M06, 30 days), July (M07, 31 days), August (M08, 31 days), September (M09, 30 days), October (M10, 31 days), November (M11, 30 days), December (M12, 31 days).

In leap years (years divisible by 4), February gains a 29th day.

Standard years thus have 365 days, and leap years 366.

Calendar drift

The Julian calendar has an average year length of 365.25, slightly longer than the mean solar year, so this calendar drifts 1 day in ~128 years with respect to the seasons. This significant drift was the reason for its replacement by the Gregorian calendar. The Julian calendar is currently 14 days ahead of the Gregorian calendar and the solar year.

Historical accuracy

Historically, a variety of year reckoning schemes have been used with the Julian calendar, such as Roman consular years, regnal years, indictions, Anno Mundi, the Diocletian era, Anno Domini, and the (equivalent) Common era. The latter, which is used today and by this implementation, has been used by western European authorities since the early middle ages, however some eastern European countries/churches have not adopted it until fairly recently, or, in some cases, are still using a different year reckoning scheme.

Also during the middle ages, some countries used different dates for the first day of the year, ranging from late December to late March. Care has to be taken when interpreting year numbers with dates in this range.

The calendar was used incorrectly for a while after adoption, so the first year where the months align with this proleptic implementation is probably 4 CE.

Implementations

impl Julian

pub fn new() -> Self

Construct a new Julian Calendar

pub fn easter(year: i32) -> Date<Self>

Returns the date of (Orthodox) Easter in the given year.

Trait Implementations

impl Calendar for Julian

fn year_info(&self, date: &Self::DateInner) -> Self::Year

The calendar-specific year represented by date Julian has the same era scheme as Gregorian

fn month(&self, date: &Self::DateInner) -> MonthInfo

The calendar-specific month represented by date

fn day_of_month(&self, date: &Self::DateInner) -> DayOfMonth

The calendar-specific day-of-month represented by date

type DateInner = JulianDateInner

The internal type used to represent dates

type Year = EraYear

The type of YearInfo returned by the date

type DifferenceError = Infallible

The type of error returned by until

fn from_codes( &self, era: Option<&str>, year: i32, month_code: MonthCode, day: u8, ) -> Result<Self::DateInner, DateError>

Construct a date from era/month codes and fields

fn from_rata_die(&self, rd: RataDie) -> Self::DateInner

Construct the date from a RataDie

fn to_rata_die(&self, date: &Self::DateInner) -> RataDie

Obtain a RataDie from this date

fn has_cheap_iso_conversion(&self) -> bool

Whether from_iso/to_iso is more efficient than from_rata_die/to_rata_die.

fn months_in_year(&self, date: &Self::DateInner) -> u8

Count the number of months in a given year, specified by providing a date from that year

fn days_in_year(&self, date: &Self::DateInner) -> u16

Count the number of days in a given year, specified by providing a date from that year

fn days_in_month(&self, date: &Self::DateInner) -> u8

Count the number of days in a given month, specified by providing a date from that year/month

fn is_in_leap_year(&self, date: &Self::DateInner) -> bool

Calculate if a date is in a leap year

fn day_of_year(&self, date: &Self::DateInner) -> DayOfYear

Information of the day of the year

fn debug_name(&self) -> &'static str

Obtain a name for the calendar for debug printing

fn calendar_algorithm(&self) -> Option<CalendarAlgorithm>

Returns the CalendarAlgorithm that is required to match when parsing into this calendar.

fn from_iso(&self, iso: IsoDateInner) -> Self::DateInner

Construct the date from an ISO date.

fn to_iso(&self, date: &Self::DateInner) -> IsoDateInner

Obtain an ISO date from this date.

fn extended_year(&self, date: &Self::DateInner) -> i32

The extended year.

impl Clone for Julian

fn clone(&self) -> Julian

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl DateFieldsResolver for Julian

type YearInfo = i32

This stores the year as either an i32, or a type containing more useful computational information.

fn days_in_provided_month(year: i32, month: u8) -> u8

fn months_in_provided_year(_: i32) -> u8

fn year_info_from_era( &self, era: &[u8], era_year: i32, ) -> Result<Self::YearInfo, UnknownEraError>

Converts the era and era year to a YearInfo. If the calendar does not have eras, this should always return an Err result.

fn year_info_from_extended(&self, extended_year: i32) -> Self::YearInfo

Converts an extended year to a YearInfo.

fn reference_year_from_month_day( &self, month_code: ValidMonthCode, day: u8, ) -> Result<Self::YearInfo, EcmaReferenceYearError>

Calculates the ECMA reference year for the month code and day, or an error if the month code and day are invalid.

fn ordinal_month_from_code( &self, _year: &Self::YearInfo, month_code: ValidMonthCode, _options: DateFromFieldsOptions, ) -> Result<u8, MonthCodeError>

Calculates the ordinal month for the given year and month code.

fn month_code_from_ordinal( &self, _year: &Self::YearInfo, ordinal_month: u8, ) -> ValidMonthCode

Calculates the month code from the given ordinal month and year.

impl Debug for Julian

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for Julian

fn default() -> Julian

Returns the “default value” for a type.

impl Hash for Julian

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl Ord for Julian

fn cmp(&self, other: &Julian) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl PartialEq for Julian

fn eq(&self, other: &Julian) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialOrd for Julian

fn partial_cmp(&self, other: &Julian) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

Tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl Copy for Julian

impl Eq for Julian

impl StructuralPartialEq for Julian