Test

local time_url = "http://www.timeapi.org/pdt/now?\\Q"
local filename_url = "http://www.timeapi.org/pdt/now?\\Y-\\m-\\d%23\\H"
if not fs.exists(".logs") then
    fs.makeDir(".logs")
end
-- Time
local realTime = tonumber(http.get(time_url).readAll())
local osTime = os.clock()
local lagAdjust = 1
local function getTime()
    return realTime/1000 + (os.clock() - osTime)*lagAdjust
end
local logname = ".logs/"..http.get(filename_url).readAll()
local logfile = io.open(logname, "a")
local loghour = math.floor(((realTime/1000)%86400)/3600)
local notLogged = {}
local function log(line)
    local hr = math.floor((getTime()%86400)/3600)
    if hr ~= loghour then
        if #notLogged == 0 then
            http.request(filename_url)
        end
        table.insert(notLogged)
    else
        logfile:write(line.."\n")
    end
end
local function pad(s, n, char)
    char = char or "0"
    return char:rep(n-tostring(s):len())..s
end
term.clear()
term.setCursorPos(1, 1)
local timer = os.startTimer(60)
local terminated = false
while true do
    local e = {os.pullEventRaw()}
    if e[1] == "chat_message" or e[1] == "chatbox_command" then
        if e[1] == "chatbox_command" then e[4] = "##"..e[4] end
        local t = getTime()
  local timestamp = "[" ..pad(math.floor((t%86400)/3600),2)..":"..pad(math.floor((t%3600)/60),2)..":"..pad(math.floor((t%60)),2).."] "
        local sender = e[3]..": "
        local message = e[4]
        term.setTextColor(colors.yellow)
        write(timestamp)
        term.setTextColor(colors.red)
        write(sender)
        term.setTextColor(colors.white)
        print(message)
        log(timestamp..sender..message)
    elseif e[1] == "http_success" then
        if e[2] == time_url then
            local t = tonumber(e[3].readAll())
            if t then
                now = os.clock()
                lagAdjust = ((t-realTime)/1000) / (now-osTime)
            realTime = t
                osTime = now
            end
        elseif e[2] == filename_url then
            logfile:close()
        logname = ".logs/"..e[3].readAll()
            logfile = io.open(logname, "a")
            loghour = math.floor((getTime()%86400)/3600)
   for i=1,#notLogged do
                logfile:write(notLogged[i].."\n")
            end
            if terminated then break end
            notLogged = {}
   end
    elseif e[1] == "http_failure" and e[2] == filename_url and terminated then
        term.setTextColor(colors.red)
        print("Could not log "..#notLogged.." messages")
        break
    elseif e[1] == "timer" and e[2] == timer then
        http.request(time_url)
        timer = os.startTimer(60)
    elseif e[1] == "terminate" then
        if #notLogged == 0 then
            break
        else
            term.setTextColor(colors.orange)
            print("Waiting for logging to finish...")
            terminated = true
        end
    end
end
print("Exiting...")
logfile:close()