Enum DateFormat 

pub enum DateFormat {
    Ymd {
        sep: char,
    },
    Mdy {
        sep: char,
        year_len: usize,
    },
    Dmy {
        sep: char,
        year_len: usize,
    },
    DMmmY {
        sep: char,
        year_len: usize,
        month_case: StringCase,
        month_full: bool,
    },
    MmmDY {
        sep: char,
        year_len: usize,
        month_case: StringCase,
        month_full: bool,
    },
    YMmmD {
        sep: char,
        year_len: usize,
        month_case: StringCase,
        month_full: bool,
    },
    Md {
        sep: char,
    },
    My {
        sep: char,
        year_len: usize,
    },
    DMmm {
        sep: char,
        month_case: StringCase,
        month_full: bool,
    },
    MmmD {
        sep: char,
        month_case: StringCase,
        month_full: bool,
    },
    MmmY {
        sep: char,
        year_len: usize,
        month_case: StringCase,
        month_full: bool,
    },
    YMmm {
        sep: char,
        year_len: usize,
        month_case: StringCase,
        month_full: bool,
    },
}

The notation a date was written in: field order, separator, year width and month-name spelling.

This is detection output, not the storage form. A cell stores an Excel serial plus the format code this lowers to (CellStyle::num_format), which is why a DateFormat can express a little more than survives a save – month-name casing has no format-code equivalent, and zero-padding of a numeric month or day is not recorded at all, so 06/22/2026 and 6/22/2026 are the same variant and both render unpadded.

The two-part variants fill in the missing field: a month/day pair takes parse_date’s default year, a month/year pair takes day 1.

Variants

Ymd

Year-month-day, all numeric: 2026-06-22.

Fields

sep: char

Character separating the fields, - or /.

Mdy

Month-day-year, all numeric: 06/22/2026, 6/22/26.

Fields

sep: char

Character separating the fields, - or /.

year_len: usize

Digits the year was written with: 2 or 4.

Dmy

Day-month-year, all numeric: 22-06-2026.

Fields

sep: char

Character separating the fields, - or /.

year_len: usize

Digits the year was written with: 2 or 4.

DMmmY

Day, month name, year: 22-Jun-2026, 22-June-26.

Fields

sep: char

Character separating the fields, - or /.

year_len: usize

Digits the year was written with: 2 or 4.

month_case: StringCase

Casing the month name was typed in.

month_full: bool

true for a full name (June), false for an abbreviation (Jun).

MmmDY

Month name, day, year: Jun-22-2026, June-22-26.

Fields

sep: char

Character separating the fields, - or /.

year_len: usize

Digits the year was written with: 2 or 4.

month_case: StringCase

Casing the month name was typed in.

month_full: bool

true for a full name (June), false for an abbreviation (Jun).

YMmmD

Year, month name, day: 2026-Jun-22.

Fields

sep: char

Character separating the fields, - or /.

year_len: usize

Digits the year was written with: 2 or 4.

month_case: StringCase

Casing the month name was typed in.

month_full: bool

true for a full name (June), false for an abbreviation (Jun).

Md

Numeric month and day, year assumed: 6/22.

Fields

sep: char

Character separating the fields, - or /.

My

Numeric month and year, day assumed to be the 1st: 6/2026.

Fields

sep: char

Character separating the fields, - or /.

year_len: usize

Digits the year was written with: 2 or 4.

DMmm

Day then month name, year assumed: 22-Jun.

Fields

sep: char

Character separating the fields, - or /.

month_case: StringCase

Casing the month name was typed in.

month_full: bool

true for a full name (June), false for an abbreviation (Jun).

MmmD

Month name then day, year assumed: Jun-22.

Fields

sep: char

Character separating the fields, - or /.

month_case: StringCase

Casing the month name was typed in.

month_full: bool

true for a full name (June), false for an abbreviation (Jun).

MmmY

Month name then year, day assumed to be the 1st: Jun-2026.

Fields

sep: char

Character separating the fields, - or /.

year_len: usize

Digits the year was written with: 2 or 4.

month_case: StringCase

Casing the month name was typed in.

month_full: bool

true for a full name (June), false for an abbreviation (Jun).

YMmm

Year then month name, day assumed to be the 1st: 2026-Jun.

Fields

sep: char

Character separating the fields, - or /.

year_len: usize

Digits the year was written with: 2 or 4.

month_case: StringCase

Casing the month name was typed in.

month_full: bool

true for a full name (June), false for an abbreviation (Jun).

Implementations

impl DateFormat

pub fn to_format_code(&self) -> String

Lowers to an Excel number-format code (m/d/yy, d-mmm-yyyy, …).

This is the interchange form: it is what gets written to the worksheet as a numFmt and what render_date_code consumes. Month-name casing has no representation in a format code, so it rides alongside as DateFormat::month_case.

pub fn month_case(&self) -> StringCase

The casing the month name was typed in, for the formats that have one.

Trait Implementations

impl Clone for DateFormat

fn clone(&self) -> DateFormat

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for DateFormat

impl Debug for DateFormat

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

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for DateFormat

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Eq for DateFormat

impl PartialEq for DateFormat

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

Equality operator ==.

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

Inequality operator !=.

impl Serialize for DateFormat

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl StructuralPartialEq for DateFormat