function toDesamber(date)
  a = {}
  for word in date:gmatch("([^-]*)") do
    a[#a+1] = tonumber(word)
  end

  year, month, day = a[1], a[2], a[3]

  daysInMonths = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}
  if ((year - 2000) % 4) == 0 then
      daysInMonths[2] = 29
  end

  daysElapsed = 0
  for i=1, month-1 do
    daysElapsed = daysElapsed + daysInMonths[i]
  end
  daysElapsed = daysElapsed + day

  if daysElapsed == 365 then
    month = "+"
    day = "01"
  elseif daysElapsed == 366 then
    month = "+"
    day = "02"
  else
    month = (daysElapsed/14)
    --print(month)
    if (month % 1) == 0 then
      month = month - 1
    end
    if month < 1 then
      month = 0
    end
    month = math.floor(month+0.5)
    month = string.upper(string.char(97+month))
  end

  return {string.sub(year, 3, 4), month, day}
end

s = ""
for k,v in pairs(toDesamber("2010-12-31")) do
  s = s .. tostring(v)
end
print(s)