/**
 * Indicates a date or string is not a valid representation of a datetime
 * according to the atproto
 * {@link https://atproto.com/specs/lexicon#datetime specification}.
 */
export declare class InvalidDatetimeError extends Error {
}
/**
 * A subset of {@link DatetimeString} that represent valid datetime strings with
 * the format: `YYYY-MM-DDTHH:mm:ss.sssZ`, as returned by `Date.toISOString()
 * for dates between the years 0000 and 9999.
 *
 * @see {@link https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/toISOString}
 */
export type ISODatetimeString = `${string}-${string}-${string}T${string}:${string}:${string}.${string}Z`;
/**
 * Represents a {@link Date} that can be safely stringified into a valid atproto
 * {@link DatetimeString} using the {@link Date.toISOString toISOString()}
 * method.
 */
export interface AtprotoDate extends Date {
    toISOString(): ISODatetimeString;
}
/**
 * @see {@link AtprotoDate}
 */
export declare function assertAtprotoDate(date: Date): asserts date is AtprotoDate;
/**
 * @see {@link AtprotoDate}
 */
export declare function asAtprotoDate(date: Date): AtprotoDate;
/**
 * @see {@link AtprotoDate}
 */
export declare function isAtprotoDate(date: Date): date is AtprotoDate;
/**
 * @see {@link AtprotoDate}
 */
export declare function ifAtprotoDate(date: Date): AtprotoDate | undefined;
/**
 * Datetime strings in atproto data structures and API calls should meet the
 * {@link https://ijmacd.github.io/rfc3339-iso8601/ intersecting} requirements
 * of the RFC 3339, ISO 8601, and WHATWG HTML datetime standards.
 *
 * @note This literal template type is not accurate enough to ensure that a
 * string is a valid atproto datetime. The {@link DatetimeString} validation
 * functions ({@link assertDatetimeString}, {@link isDatetimeString}, etc)
 * should be used to validate that a string meets the atproto datetime
 * requirements, and the {@link toDatetimeString} function should be used to
 * convert a {@link Date} object into a valid {@link DatetimeString} string.
 *
 * @example "2024-01-15T12:30:00Z"
 * @example "2024-01-15T12:30:00.000Z"
 * @example "2024-01-15T12:30:00+00:00"
 * @example "2024-01-15T11:30:00-01:00"
 * @see {@link https://atproto.com/specs/lexicon#datetime atproto Lexicon datetime format}
 * @see {@link https://www.rfc-editor.org/rfc/rfc3339 RFC 3339}
 * @see {@link https://www.iso.org/iso-8601-date-and-time-format.html ISO 8601}
 */
export type DatetimeString = `${string}-${string}-${string}T${string}:${string}:${string}Z` | `${string}-${string}-${string}T${string}:${string}:${string}${'+' | '-'}${string}:${string}`;
/**
 * Validates that a string is a valid {@link DatetimeString} format string,
 * throwing an error if it is not.
 *
 * @throws InvalidDatetimeError if the input string does not meet the atproto 'datetime' format requirements.
 * @see {@link DatetimeString}
 */
export declare function assertDatetimeString<I>(input: I): asserts input is I & DatetimeString;
/**
 * Casts a string to a {@link DatetimeString} if it is a valid datetime format
 * string, throwing an error if it is not.
 *
 * @throws InvalidDatetimeError if the input string does not meet the atproto 'datetime' format requirements.
 * @see {@link DatetimeString}
 */
export declare function asDatetimeString<I>(input: I): I & DatetimeString;
/**
 * Checks if a string is a valid {@link DatetimeString} format string.
 *
 * @see {@link DatetimeString}
 */
export declare function isDatetimeString<I>(input: I): input is I & DatetimeString;
/**
 * Returns the input if it is a valid {@link DatetimeString} format string, or
 * `undefined` if it is not.
 *
 * @see {@link DatetimeString}
 */
export declare function ifDatetimeString<I>(input: I): undefined | (I & DatetimeString);
/**
 * Returns the current date and time as a {@link DatetimeString}.
 *
 * @see {@link DatetimeString}
 */
export declare function currentDatetimeString(): DatetimeString;
/**
 * Converts any {@link Date} into a {@link DatetimeString} if possible, throwing
 * an error if the date is not a valid atproto datetime.
 *
 * This is short-hand for `asAtprotoDate(date).toISOString()`.
 *
 * @throws InvalidDatetimeError if the input date is not a valid atproto datetime (eg, it is too far in the future or past, or it normalizes to a negative year).
 * @see {@link DatetimeString}
 */
export declare function toDatetimeString(date: Date): DatetimeString;
/**
 * Takes a flexible datetime string and normalizes its representation.
 *
 * This function will work with any valid value that can be parsed as a date. It
 * *additionally* is more flexible about accepting datetimes that are missing
 * timezone information, and normalizing them to a valid atproto datetime.
 *
 * One use-case is a consistent, sortable string. Another is to work with older
 * invalid createdAt datetimes.
 *
 * @note This function might return different normalized strings for the same
 * input depending on the timezone of the machine it is run on, since it will
 * attempt to parse the input "as is" if it fails to parse with an explicit
 * timezone.
 *
 * @returns ISODatetimeString - a valid atproto datetime with millisecond precision (3 sub-second digits) and UTC timezone with trailing 'Z' syntax.
 * @throws InvalidDatetimeError - if the input string could not be parsed as a datetime, even with permissive parsing.
 */
export declare function normalizeDatetime(dtStr: string): ISODatetimeString;
/**
 * Variant of {@link normalizeDatetime} which always returns a valid datetime
 * string.
 *
 * If a {@link InvalidDatetimeError} is encountered, returns the UNIX epoch time
 * as a UTC datetime (`1970-01-01T00:00:00.000Z`).
 *
 * @see {@link normalizeDatetime}
 */
export declare function normalizeDatetimeAlways(dtStr: string): ISODatetimeString;
export { assertDatetimeString as ensureValidDatetime, isDatetimeString as isValidDatetime, };
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