Module:Sandbox/R1F4T

local p = {}

local function isLeapYear(y)
	return ((y - 594) % 4 == 0)  -- Simple Bengali leap year rule
end

local function toBengaliNumber(num)
	local bnDigits = {'০','১','২','৩','৪','৫','৬','৭','৮','৯'}
	return tostring(num):gsub("%d", function(d) return bnDigits[tonumber(d)+1] end)
end

function p.unixToBengaliDate(frame)
	local timestamp = tonumber(frame.args[1])
	local second = 86400
	local days = math.floor(timestamp / second)

	local year = 1432  -- Start from 1 Boishakh 1432
	while true do
		local leap = isLeapYear(year) and 366 or 365
		if days < leap then break end
		days = days - leap
		year = year + 1
	end

	local isLeap = isLeapYear(year)
	local monthLengths = {31,31,31,31,31,31,30,30,30,30,30, isLeap and 30 or 29}
	local month = 1

	while days >= monthLengths[month] do
		days = days - monthLengths[month]
		month = month + 1
	end

	local day = days + 1

	return string.format("%s-%s-%s", toBengaliNumber(day), toBengaliNumber(month), toBengaliNumber(year))
end

return p