How would I allow players to increase in rank based on how long they have played the game?

How would I allow players to increase in rank based on how long they have played the game? For example, if a player has previously played the game for 1 hour and plays for 1 hour the next day and because they have played the game for altogether two hours they can move up a rank.

I don't know how to make ranks for a player like 1 Newbie 2 Citizen etc

Thank you and help is appreciated

You could probably use a script in the players' starterpack to increase a (leaderstats) value added every minute or so like this:

while wait(60) do
	player.TimeInGame.Value = player.TimeInGame.Value + 1
	if (player.TimeInGame.Value == timeNeededToRankUp) then
		-- Do things with rank up here
	end
end

and use ROBLOX DataStore to Save/Load user data when they join/leave the game. If you do decide to use DataStore, be cautious that you aren't calling :GetAsync() and :SetAsync() too much, as there is a limit based on the number of players in your place.

I'm not 100% knowledgeable about this sort of thing, but this is how I would approach this problem. Hope it helps!