How to get account age from UserID?

The AccountAge is a Player property that describes how long ago a player’s account was registered in days. It is set using the Player:SetAccountAge function, which cannot be accessed by scripts.

This property is useful for conditionally showing new Roblox players content such as tutorials.

for example:

local Players = game:GetService("Players")

local MAX_AGE_NEW_PLAYER = 7 -- a week
local MIN_AGE_VETERAN = 365 -- one year

-- This function marks a part with text using a BillboardGui
local function mark(part, text)
    local bbgui = Instance.new("BillboardGui")
    bbgui.AlwaysOnTop = true
    bbgui.StudsOffsetWorldSpace = Vector3.new(0, 2, 0)
    bbgui.Size = UDim2.new(0, 200, 0, 50)
    local textLabel = Instance.new("TextLabel")
    textLabel.Size = UDim2.new(1, 0, 1, 0) -- Fill parent
    textLabel.Text = text
    textLabel.TextColor3 = Color3.new(1, 1, 1)
    textLabel.TextStrokeTransparency = 0
    textLabel.BackgroundTransparency = 1
    textLabel.Parent = bbgui
    -- Add to part
    bbgui.Parent = part
    bbgui.Adornee = part
end

local function onPlayerSpawned(player, character)
    local head = character:WaitForChild("Head")
    if player.AccountAge >= MIN_AGE_VETERAN then
        mark(head, "Veteran Player")
    elseif player.AccountAge <= MAX_AGE_NEW_PLAYER then
        mark(head, "New Player")
    else
        mark(head, "Regular Player")
    end
end

local function onPlayerAdded(player)
    -- Listen for this player spawning
    if player.Character then
        onPlayerSpawned(player, player.Character)
    end
    player.CharacterAdded:Connect(function ()
        onPlayerSpawned(player, player.Character)
    end)
end

-- Listen for players being added
for _, player in pairs(Players:GetPlayers()) do
    onPlayerAdded(player)
end
Players.PlayerAdded:Connect(onPlayerAdded)