This version assumes that it is displayed in a page that will set padding/margins/gutters in parent containing elements. It will expand to a maximum of 350px wide and remain centered in the column. It includes a link to the full month's page in the footer. Only the six most recent days of the month will have hyperlinks, reflecting the 6 most recent days of content on the Portal:Current events page.
This version assumes that it is displayed in a page that uses a table-based layout and expect individual children to set their margins and padding. It will expand to a maximum of 350px wide and puts an 8px margin on the top and left side of the calendar. It has no footer. All days will have links to the appropriate section of the page it is displayed in.
-- This module renders the calendar seen on [[Portal:Current events]].
--[[
	Incoming expected variables:
		frame.args.year = Integer value for year
		frame.args.month = Integer value for month, 1 based.
--]]
local p = {}
local function makeWikilink(link, display)
	if display then
		return string.format('[[%s|%s]]', link, display)
	else
		return string.format('[[%s]]', link)
	end
end
local function getDateStuff(argsDate)
--[[
	Note: This function takes advantage of the formatDate's second argument to
	create data for the archival calendars. If the second arg (argsDate) is nil,
	then formatDate assumes the current date/time.
--]]
	local lang = mw.language.getContentLanguage()
	local firstOfMonth = lang:formatDate('01-m-Y', argsDate)
	return {
		argsDate = argsDate,
		year = tonumber(lang:formatDate('Y', argsDate)),
		month = lang:formatDate('F', argsDate),
		monthAndYear = lang:formatDate('F Y', argsDate),
		previousMonthAndYear = lang:formatDate('F Y', firstOfMonth .. ' -1 month'),
		nextMonthAndYear = lang:formatDate('F Y', firstOfMonth .. ' +1 month'),
		day = tonumber(lang:formatDate('j', argsDate)),
		daysInMonth = tonumber(lang:formatDate('j', firstOfMonth .. ' +1 month -1 day')),
		-- Weekday of the first day of the month
		-- Make compatible with Lua tables so we add 1. Sunday = 1, Saturday = 7.
		firstWeekday = tonumber(lang:formatDate('w', firstOfMonth)) + 1
	}
end
local function isLinkworthy(day, currentDay)
	-- Returns true if the calendar day should be linked, and false if not. Days
	-- should be linked if they are the current day or if they are within the six
	-- preceding days, as that is the number of items on the current events page.
	return currentDay - 6 <= day and day <= currentDay
end
local function makeDayStrings(dateStuff)
	local calStrings = {}
	local currentDay = dateStuff.day
	local currentMonth = dateStuff.month
	local currentYear = dateStuff.year
	for day = 1, dateStuff.daysInMonth do
		if dateStuff.argsDate or isLinkworthy(day, currentDay) then
			table.insert(calStrings, string.format(
				"[[#%d %s %d|%d]]",
				currentYear,
				currentMonth,
				day,
				day
			))
		else
			table.insert(calStrings, tostring(day))
		end
	end
	return calStrings
end
local function export(dayStrings, dateStuff)
	-- Generates the calendar HTML.
	local monthAndYear = dateStuff.monthAndYear
	local root = mw.html.create('table')
	root
		:addClass('current-events-calendar')
		-- Make the table-layout-based Archive pages look good. When the Archives
		-- have been converted to a grid-based layout, this logic can be removed,
		-- and the corressponding CSS margin attribute can be simplified.
		:addClass(dateStuff.argsDate and 'current-events-calendar-archive')
		-- Headings
		:tag('caption')
			:tag('span')
				:addClass('noprint')
				:wikitext(makeWikilink(
					'Portal:Current events/' .. dateStuff.previousMonthAndYear,
					'◀'
				))
				:done()
			:tag('span')
				:wikitext(makeWikilink(
					'Portal:Current events/' .. monthAndYear,
					monthAndYear
				))
				:done()
			:tag('span')
				:addClass('noprint')
				:wikitext(makeWikilink(
					'Portal:Current events/' .. dateStuff.nextMonthAndYear,
					'▶'
				))
	-- Day of week headings
	local dayHeadingRow = root:tag('tr')
	local weekdays = {'S', 'M', 'T', 'W', 'T', 'F', 'S'}
	for _, weekday in ipairs(weekdays) do
		dayHeadingRow:tag('th'):wikitext(weekday)
	end
	-- Days
	-- Tracks the number of day cells. Negative values used for initial blank cells.
	local cellCount = 1 - dateStuff.firstWeekday
	while cellCount < #dayStrings do -- Weekly rows
		local weeklyRow = root:tag('tr')
		for i = 1, 7 do -- Always make 7 cells.
			cellCount = cellCount + 1
			-- Use a blank cell if there is no corresponding dateString
			local dayString = dayStrings[cellCount] or ''
			weeklyRow:tag('td'):wikitext(dayString)
		end
	end
	-- Footer
	if not dateStuff.argsDate then -- No footer necessary on Archive pages.
		root:tag('tr')
			:addClass('current-events-calendar-footer')
		    :addClass('noprint')
			:tag('td')
				:attr('colspan', '7')
				:wikitext(makeWikilink(
					'Portal:Current events/' .. monthAndYear,
					'More ' .. monthAndYear .. ' events...   '
				))
	end
	
	return tostring(root)
end
function p.main(frame)
	local argsDate = nil
	if frame and frame.args and frame.args.year and frame.args.month then
		-- If a date is passed in, assume that the display page is an Archive page.
		-- If no date passed in, assume that the display page is the current Current Events page
		-- Construct a date, YYY-M-DD format.
		argsDate = frame.args.year .. "-" .. frame.args.month .. "-01"
	end
	local dateStuff = getDateStuff(argsDate)
	return frame:extensionTag{
		name = 'templatestyles',
		args = { src = 'Module:Current events calendar/styles.css' }
	} .. export(makeDayStrings(dateStuff), dateStuff)
end
return p