Uses liquid flows (water and lava) to determine if chunk is newly generated. Chunk status is displayed on Exploration Mini Map.
Red squares - old chunks (chunks contains non-source water/lava blocks)
Green squares - new chunks (chunk didn't have non-source water/lava blocks, but server sent block update packets with non-source water/lava)
Yelllow squares - relatively new chunks (chunk already had non-source water/lava, but new non-source water/lava blocks appeared)
Chunk without square - there is no water/lava to guess chunk status