export function easter ( y , offset = 0 ) { const a = y % 19 ; const b = Math . floor ( y / 100 ) ; const c = y % 100 ; const d = Math . floor ( b / 4 ) ; const e = b % 4 ; const f = Math . floor ( ( b + 8 ) / 25 ) ; const g = Math . floor ( ( b - f + 1 ) / 3 ) ; const h = Math . floor ( 19 * a + b - d - g + 15 ) % 30 ; const i = Math . floor ( c / 4 ) ; const k = c % 4 ; const l = Math . floor ( 32 + 2 * e + 2 * i - h - k ) % 7 ; const m = Math . floor ( ( a + 11 * h + 22 * l ) / 451 ) ; const month = Math . floor ( ( h + l - 7 * m + 114 ) / 31 ) ; const day = ( ( h + l - 7 * m + 114 ) % 31 ) + 1 ; const date = Date . UTC ( y , month - 1 , day + offset ) ; const yearStart = Date . UTC ( y , 0 , 1 ) ; return [ Math . ceil ( ( date - yearStart ) / ( 1000 * 60 * 60 * 24 ) ) ] ; }