Add year removal support

[ligiapopescu]

Summary

• add optional omitYear formatting option to DateTimeFormatter.formatDateTime
• add internal year-removal helper for locale-aware OS mask cleanup
• preserve explicit WITH_YEAR behavior in OS switch handling
• add direct year-removal unit tests and expand formatter tests
• document the new API usage in README

Validation

• yarn lint
• yarn test
• yarn build

[Copilot]

Pull request overview

Adds an omitYear formatting option to allow locale-aware year removal from date masks and Intl formatting, with supporting helper logic, tests, and documentation.

Changes:

• Introduced removeYearFromMask() with locale-aware dot-separator handling.
• Extended DateTimeFormatter to accept an omitYear option across Intl and OS formatting paths.
• Added targeted unit tests for year removal and expanded formatter tests, plus README usage docs.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
src/year-removal.ts	Adds the locale-aware mask year-removal helper and locale dot-preservation rules.
src/year-removal.test.ts	Adds direct unit coverage for year-removal behavior across locales.
src/date-time-formatter.ts	Threads omitYear through formatting paths and applies year-stripping logic.
src/date-time-formatter.test.ts	Adds integration tests verifying omitYear behavior for OS/Intl paths.
README.md	Documents the new options.omitYear API parameter.

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[Copilot]

omitYearis currently applied toSHORT_DATE_WITH_SHORT_YEAR/SHORT_DATE_WITH_YEARin the OS-formatting switch viagetDateMask(..., omitYear), but the new tests assert that WITH_YEAR OS formats must *not* omit the year. To match the intended behavior, ignore omitYearfor these WITH_YEAR cases (e.g., passfalsetogetDateMaskhere, or bypassgetDateMaskand uselocaleInfo.shortDate` directly for these formats).

[Copilot]

removeYearFromMask()can return masks with leading/trailing whitespace artifacts (and sometimes doubled spaces) after removal (as evidenced by several unit expectations like"d. MMMM "/"d MMMM "/" d. MMMM"`). This makes the helper output inconsistently “valid” depending on how downstream formatters treat whitespace. Consider normalizing the result (e.g., trim and/or collapse repeated spaces, and remove leftover separator-adjacent whitespace) so the returned mask is stable and doesn’t depend on formatter-specific trimming behavior.

Suggested change

	export function removeYearFromMask(mask: string, localeCode: string): string {
	// Locales requiring dot-after-month use a regex variant that does not strip leading dots.
	const regex = doesLocaleRequireDotAfterMonth(localeCode)
	? NO_YEAR_REGEX
	: NO_YEAR_REGEX_REMOVE_DOT_AFTER_MONTH;
	return mask.replace(regex, "");
	function normalizeMaskWhitespace(mask: string): string {
	// Remove whitespace immediately around common separator characters.
	let result = mask.replace(/\s*([.,\/-])\s*/g, "$1");
	// Collapse remaining consecutive whitespace to a single space and trim ends.
	result = result.replace(/\s+/g, " ").trim();
	return result;
	}
	export function removeYearFromMask(mask: string, localeCode: string): string {
	// Locales requiring dot-after-month use a regex variant that does not strip leading dots.
	const regex = doesLocaleRequireDotAfterMonth(localeCode)
	? NO_YEAR_REGEX
	: NO_YEAR_REGEX_REMOVE_DOT_AFTER_MONTH;
	const withoutYear = mask.replace(regex, "");
	return normalizeMaskWhitespace(withoutYear);

[Copilot]

The inline options?: { omitYear?: boolean } type is duplicated across public APIs. To keep the API consistent and easier to extend (e.g., if more formatting flags are added later), consider introducing a named exported type/interface (e.g., DateTimeFormatterOptions) and reusing it in both method signatures and documentation examples.