docs: function jalCalLeap (jy) {
    let bl = breaks.length,
      jp = breaks[0],
      jm,
      jump,
      leap,
      n,
      i
  
    if (jy < jp || jy >= breaks[bl - 1]) { throw new Error('Invalid Jalaali year ' + jy) }
  
    for (i = 1; i < bl; i += 1) {
      jm = breaks[i]
      jump = jm - jp
      if (jy < jm) { break }
      jp = jm
    }
    n = jy - jp
  
    if (jump - n < 6) { n = n - jump + div(jump + 4, 33) * 33 }
    leap = mod(mod(n + 1, 33) - 1, 4)
    if (leap === -1) {
      leap = 4
    }
  
    return leap
  }