diff --git a/mods/ENTITIES/mcl_mobs/init.lua b/mods/ENTITIES/mcl_mobs/init.lua
index 62100c627..a16f1c23d 100644
--- a/mods/ENTITIES/mcl_mobs/init.lua
+++ b/mods/ENTITIES/mcl_mobs/init.lua
@@ -287,6 +287,7 @@ function mcl_mobs.register_mob(name, def)
 		spawn_in_group_min = def.spawn_in_group_min,
 		noyaw = def.noyaw or false,
 		particlespawners = def.particlespawners,
+		spawn_check = def.spawn_check,
 		-- End of MCL2 extensions
 		on_spawn = def.on_spawn,
 		on_blast = def.on_blast or function(self,damage)
diff --git a/mods/ENTITIES/mcl_mobs/spawning.lua b/mods/ENTITIES/mcl_mobs/spawning.lua
index 82870dcd3..9c51c0f86 100644
--- a/mods/ENTITIES/mcl_mobs/spawning.lua
+++ b/mods/ENTITIES/mcl_mobs/spawning.lua
@@ -742,11 +742,15 @@ local function spawn_check(pos, spawn_def)
 					end
 				elseif dimension == "overworld" then
 					if mob_type == "monster" then
-						if art_light <= overworld_threshold and sky_light <= overworld_sky_threshold then
+						if mob_def.spawn_check then
+							return mob_def.spawn_check(pos, gotten_light, art_light, sky_light)
+						elseif art_light <= overworld_threshold and sky_light <= overworld_sky_threshold then
 							return true
 						end
 					else
-						if gotten_light > overworld_passive_threshold then
+						if mob_def.spawn_check then
+							return mob_def.spawn_check(pos, gotten_light, art_light, sky_light)
+						elseif gotten_light > overworld_passive_threshold then
 							return true
 						end
 					end
diff --git a/mods/ENTITIES/mobs_mc/bat.lua b/mods/ENTITIES/mobs_mc/bat.lua
index b5532e2ee..b8b650877 100644
--- a/mods/ENTITIES/mobs_mc/bat.lua
+++ b/mods/ENTITIES/mobs_mc/bat.lua
@@ -2,6 +2,18 @@
 
 local S = minetest.get_translator("mobs_mc")
 
+local function spawn_check(pos, environmental_light, artificial_light, sky_light)
+	local date = os.date("*t")
+	local maxlight
+	if (date.month == 10 and date.day >= 20) or (date.month == 11 and date.day <= 3) then
+		maxlight = 6
+	else
+		maxlight = 3
+	end
+
+	return artificial_light <= maxlight
+end
+
 mcl_mobs.register_mob("mobs_mc:bat", {
 	description = S("Bat"),
 	type = "animal",
@@ -50,6 +62,7 @@ mcl_mobs.register_mob("mobs_mc:bat", {
 	jump = false,
 	fly = true,
 	makes_footstep_sound = false,
+	spawn_check = spawn_check,
 })
 
 
diff --git a/mods/ENTITIES/mobs_mc/slime+magma_cube.lua b/mods/ENTITIES/mobs_mc/slime+magma_cube.lua
index c07afb6b1..9cc5191bc 100644
--- a/mods/ENTITIES/mobs_mc/slime+magma_cube.lua
+++ b/mods/ENTITIES/mobs_mc/slime+magma_cube.lua
@@ -161,6 +161,16 @@ local spawn_children_on_die = function(child_mob, spawn_distance, eject_speed)
 	end
 end
 
+local function slime_spawn_check(pos, environmental_light, artificial_light, sky_light)
+	local maxlight = swamp_light_max
+
+	if is_slime_chunk(pos) then
+		maxlight = minetest.LIGHT_MAX + 1
+	end
+
+	return artificial_light <= maxlight
+end
+
 -- Slime
 local slime_big = {
 	description = S("Slime"),
@@ -213,6 +223,7 @@ local slime_big = {
 	spawn_small_alternative = "mobs_mc:slime_small",
 	on_die = spawn_children_on_die("mobs_mc:slime_small", 1.0, 1.5),
 	use_texture_alpha = true,
+	spawn_check = slime_spawn_check,
 }
 mcl_mobs.register_mob("mobs_mc:slime_big", slime_big)