/**
 * Returns true if the Gregorian year is a leap year
 * @param year Gregorian year
 * @example
 * isGregLeapYear(2000); // true
 * isGregLeapYear(2020); // true
 * isGregLeapYear(2023); // false
 * isGregLeapYear(2100); // false (divisible by 100 but not 400)
 */
export declare function isGregLeapYear(year: number): boolean;
/**
 * Number of days in the Gregorian month for given year
 * @param month Gregorian month (1=January, 12=December)
 * @param year Gregorian year
 * @example
 * daysInGregMonth(2, 2024); // 29 (February in a leap year)
 * daysInGregMonth(2, 2023); // 28
 * daysInGregMonth(7, 2024); // 31 (July)
 */
export declare function daysInGregMonth(month: number, year: number): number;
/**
 * Returns true if the object is a Javascript Date
 * @example
 * isDate(new Date()); // true
 * isDate('2024-01-01'); // false
 * isDate(1700000000000); // false
 */
export declare function isDate(obj: unknown): boolean;
/**
 * Converts Gregorian date to absolute R.D. (Rata Die) days
 * @param date Gregorian date
 * @example
 * greg2abs(new Date(2008, 10, 13)); // 733359 (13 November 2008)
 * greg2abs(new Date(2005, 3, 2)); // 732038 (2 April 2005)
 */
export declare function greg2abs(date: Date): number;
/**
 * Converts from Rata Die (R.D. number) to Gregorian date.
 * See the footnote on page 384 of ``Calendrical Calculations, Part II:
 * Three Historical Calendars'' by E. M. Reingold,  N. Dershowitz, and S. M.
 * Clamen, Software--Practice and Experience, Volume 23, Number 4
 * (April, 1993), pages 383-404 for an explanation.
 *
 * Note that this function returns the daytime portion of the date.
 * For example, the 15th of Cheshvan 5769 began at sundown on
 * 12 November 2008 and continues through 13 November 2008. This
 * function would return only the date 13 November 2008.
 * @param abs - R.D. number of days
 * @example
 * const abs = hebrew2abs(5769, months.CHESHVAN, 15);
 * const date = abs2greg(abs); // 13 November 2008
 * const year = date.getFullYear(); // 2008
 * const monthNum = date.getMonth() + 1; // 11
 * const day = date.getDate(); // 13
 */
export declare function abs2greg(abs: number): Date;