/** How an occasion repeats. `annual` is the ordinary case; `once` never returns. */
export type OccasionRecurrence = 'annual' | 'once';
/**
 * A parsed occasion date.
 *
 * `recurring` has no year because the year is meaningless for an annual date and
 * carrying one invites arithmetic that uses it. `dated` has one because a `once`
 * occasion without a year is not a date at all.
 */
export type OccasionDate = {
    readonly kind: 'recurring';
    readonly month: number;
    readonly day: number;
} | {
    readonly kind: 'dated';
    readonly year: number;
    readonly month: number;
    readonly day: number;
};
/** `YYYY-MM-DD`, the only date representation that crosses a module boundary here. */
export type IsoDate = string;
/** Days in a month, 1-based, honouring the leap rule. */
export declare function daysInMonth(year: number, month: number): number;
export declare function isLeapYear(year: number): boolean;
/**
 * Parse `MM-DD` or `YYYY-MM-DD`, or `null` for anything else.
 *
 * The calendar is checked, not just the shape: `02-30` and `2026-13-01` are
 * refused. That matters because an occasion whose date does not exist would
 * otherwise sit in the file looking healthy and never fire, and "it never
 * reminded me" is the failure this whole feature exists to prevent.
 */
export declare function parseOccasionDate(value: string): OccasionDate | null;
/** Render a date back to the form it is written in. Inverse of the parser. */
export declare function renderOccasionDate(date: OccasionDate): string;
export declare function toIsoDate(year: number, month: number, day: number): IsoDate;
/**
 * The occurrence of `date` in `year`, with 29 February landing on the 28th.
 *
 * Owner-facing consequence: in a non-leap year a 29 February birthday is raised
 * on the 28th rather than skipped. Skipping is the behaviour a naive
 * implementation produces (the date simply does not exist, so nothing matches)
 * and it means the feature silently does nothing three years in four for the
 * person it was built for. Landing early is a day out; landing never is the
 * whole failure.
 */
export declare function occurrenceInYear(date: OccasionDate, year: number): IsoDate;
/**
 * The next occurrence on or after `today`, or `null` when there is not one.
 *
 * A `once` occasion that has passed returns `null`, it is over, and an
 * occasion that keeps proposing a date in the past would nudge forever.
 * An `annual` occasion always has a next one.
 */
export declare function nextOccurrence(date: OccasionDate, recurrence: OccasionRecurrence, today: IsoDate): IsoDate | null;
/**
 * Whole days from `from` to `to`, negative when `to` is earlier.
 *
 * Computed through `Date.UTC` on the parsed parts rather than by parsing the
 * strings as instants: `new Date('2026-03-14')` is UTC midnight while
 * `new Date('2026-03-14T00:00')` is local midnight, and mixing the two puts the
 * count a day out for half the planet. Both ends are calendar dates already in
 * the owner's zone by the time they reach here, so UTC is simply the arithmetic
 * frame and carries no zone meaning at all.
 */
export declare function daysBetween(from: IsoDate, to: IsoDate): number;
/** `iso` shifted by `days`, still a calendar date. */
export declare function addDays(iso: IsoDate, days: number): IsoDate;
/** True when `iso` parses as a calendar date that exists. */
export declare function isIsoDate(value: string): boolean;
/** The calendar day it is where the owner is, from `daemon.timezone`. */
export declare function todayInZone(nowMs: number, timezone: string): IsoDate;
/**
 * Minutes past midnight where the owner is.
 *
 * `hourCycle: 'h23'` and `formatToParts` together, rather than slicing a
 * formatted string: an `en-US` time format is 12-hour by default, so a naive
 * slice reads 10pm as minute 600 and puts the quiet-hours boundary fourteen
 * hours out, in the direction that sends a message at 10pm believing it is
 * 10am.
 */
export declare function minutesOfDayInZone(nowMs: number, timezone: string): number;
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