diff --git a/include/config/overworld.h b/include/config/overworld.h
index cebbe5b34b..8be52abfb5 100644
--- a/include/config/overworld.h
+++ b/include/config/overworld.h
@@ -74,6 +74,13 @@
 #define OW_USE_FAKE_RTC                 FALSE      // When TRUE, seconds on the in-game clock will only advance once every 60 playTimeVBlanks (every 60 frames).
 #define OW_ALTERED_TIME_RATIO           GEN_LATEST // In GEN_8_PLA, the time in game moves forward 60 seconds for every second in the RTC. In GEN_9, it is 20 seconds. This has no effect if OW_USE_FAKE_RTC is FALSE.
 
+// Time-based wild Pokemon encounters - Allows you to create additional encounter groups in wild_encounters.json (or in porymap). 
+// The groups are processed by base label's suffix. For example, "gRoute101" (no suffix) contains daytime encounters, and "gRoute101_Night" contains nighttime encounters.
+// Not every group needs to be defined for every map - you could for example omit them inside caves and it would fall back to the unsuffixed daytime encounter group.
+#define OW_TIME_BASED_WILD_ENCOUNTERS           FALSE // Enables the system. If disabled, all suffixes are ignored and the first encounter group found for a map will be used for wild encounters.
+#define OW_ENABLE_MORNING_WILD_ENCOUNTERS       FALSE // If true, allows definition of morning encounter groups such as "gRoute101_Morning". Otherwise, morning is considered to be day for encounters. No effect if OW_TIME_BASED_WILD_ENCOUNTERS is false.
+#define OW_ENABLE_EVENING_WILD_ENCOUNTERS       FALSE // If true, allows definition of evening encounter groups such as "gRoute101_Evening". Otherwise, evening is considered to be night for encounters. No effect if OW_TIME_BASED_WILD_ENCOUNTERS is false.
+
 // Overworld flags
 // To use the following features in scripting, replace the 0s with the flag ID you're assigning it to.
 // Eg: Replace with FLAG_UNUSED_0x264 so you can use that flag to toggle the feature.
diff --git a/include/wild_encounter.h b/include/wild_encounter.h
index 63289f081c..fb0f5ab00e 100644
--- a/include/wild_encounter.h
+++ b/include/wild_encounter.h
@@ -20,6 +20,7 @@ struct WildPokemonHeader
 {
     u8 mapGroup;
     u8 mapNum;
+    u8 timeOfDay;
     const struct WildPokemonInfo *landMonsInfo;
     const struct WildPokemonInfo *waterMonsInfo;
     const struct WildPokemonInfo *rockSmashMonsInfo;
diff --git a/src/data/wild_encounters.json.txt b/src/data/wild_encounters.json.txt
index bf848249f0..55dd20cd52 100755
--- a/src/data/wild_encounters.json.txt
+++ b/src/data/wild_encounters.json.txt
@@ -72,6 +72,7 @@ const struct WildPokemonHeader {{ wild_encounter_group.label }}[] =
     {
         .mapGroup = {% if wild_encounter_group.for_maps %}MAP_GROUP({{ removePrefix(encounter.map, "MAP_") }}){% else %}0{% endif %},
         .mapNum = {% if wild_encounter_group.for_maps %}MAP_NUM({{ removePrefix(encounter.map, "MAP_") }}){% else %}{{ loop.index1 }}{% endif %},
+        .timeOfDay = {% if stringEndsWith(encounter.base_label, "_Night") or stringContains(encounter.base_label, "_Night_") %}TIME_NIGHT{% else if stringEndsWith(encounter.base_label, "_Morning") or stringContains(encounter.base_label, "_Morning_") %}TIME_MORNING{% else if stringEndsWith(encounter.base_label, "_Evening") or stringContains(encounter.base_label, "_Evening_") %}TIME_EVENING{% else %}TIME_DAY{% endif %},
         .landMonsInfo = {% if existsIn(encounter, "land_mons") %}&{{ encounter.base_label }}_LandMonsInfo{% else %}NULL{% endif %},
         .waterMonsInfo = {% if existsIn(encounter, "water_mons") %}&{{ encounter.base_label }}_WaterMonsInfo{% else %}NULL{% endif %},
         .rockSmashMonsInfo = {% if existsIn(encounter, "rock_smash_mons") %}&{{ encounter.base_label }}_RockSmashMonsInfo{% else %}NULL{% endif %},
@@ -81,6 +82,7 @@ const struct WildPokemonHeader {{ wild_encounter_group.label }}[] =
     {
         .mapGroup = MAP_GROUP(UNDEFINED),
         .mapNum = MAP_NUM(UNDEFINED),
+        .timeOfDay = TIME_DAY,
         .landMonsInfo = NULL,
         .waterMonsInfo = NULL,
         .rockSmashMonsInfo = NULL,
diff --git a/src/wild_encounter.c b/src/wild_encounter.c
index 033eec56da..3cfdfb1191 100644
--- a/src/wild_encounter.c
+++ b/src/wild_encounter.c
@@ -11,6 +11,7 @@
 #include "pokeblock.h"
 #include "battle_setup.h"
 #include "roamer.h"
+#include "rtc.h"
 #include "tv.h"
 #include "link.h"
 #include "script.h"
@@ -354,9 +355,32 @@ static u8 ChooseWildMonLevel(const struct WildPokemon *wildPokemon, u8 wildMonIn
     }
 }
 
+static bool8 IsExactTimeOfDayMatchForWildEncounters(u8 currentTimeOfDay, u8 encounterTimeOfDay)
+{
+    switch (currentTimeOfDay)
+    {
+    case TIME_MORNING:
+        if (OW_ENABLE_MORNING_WILD_ENCOUNTERS)
+            return encounterTimeOfDay == TIME_MORNING;
+        // fallthrough
+    case TIME_DAY:
+        return encounterTimeOfDay == TIME_DAY;
+    case TIME_EVENING:
+        if (OW_ENABLE_EVENING_WILD_ENCOUNTERS)
+            return encounterTimeOfDay == TIME_EVENING;
+        // fallthrough
+    case TIME_NIGHT:
+        return encounterTimeOfDay == TIME_NIGHT;
+    }
+    return FALSE;
+}
+
 static u16 GetCurrentMapWildMonHeaderId(void)
 {
     u16 i;
+    u8 currentTimeOfDay = GetTimeOfDay();
+    u16 dayId = HEADER_NONE;
+    u16 nightId = HEADER_NONE;
 
     for (i = 0; ; i++)
     {
@@ -375,13 +399,30 @@ static u16 GetCurrentMapWildMonHeaderId(void)
                     alteringCaveId = 0;
 
                 i += alteringCaveId;
+                return i; // Altering cave is not affected by time-of-day encounters.
             }
 
-            return i;
+            if (OW_TIME_BASED_WILD_ENCOUNTERS)
+            {
+                if (IsExactTimeOfDayMatchForWildEncounters(currentTimeOfDay, gWildMonHeaders[i].timeOfDay))
+                    return i;
+                else if (gWildMonHeaders[i].timeOfDay == TIME_DAY && dayId == HEADER_NONE)
+                    dayId = i;
+                else if (gWildMonHeaders[i].timeOfDay == TIME_NIGHT && nightId == HEADER_NONE)
+                    nightId = i;
+            }
+            else
+                return i;
         }
     }
 
-    return HEADER_NONE;
+    if (!OW_TIME_BASED_WILD_ENCOUNTERS)
+        return HEADER_NONE;
+
+    // Exact match for time of day was not found. We fall back to other encounter groups for this map
+    if (currentTimeOfDay == TIME_EVENING && OW_ENABLE_EVENING_WILD_ENCOUNTERS && nightId != HEADER_NONE)
+        return nightId;
+    return dayId;
 }
 
 u8 PickWildMonNature(void)
diff --git a/tools/jsonproc/jsonproc.cpp b/tools/jsonproc/jsonproc.cpp
index 9ef23cd43e..5e661e40d3 100755
--- a/tools/jsonproc/jsonproc.cpp
+++ b/tools/jsonproc/jsonproc.cpp
@@ -118,6 +118,27 @@ int main(int argc, char *argv[])
         return str;
     });
 
+    env.add_callback("stringContains", 2, [](Arguments& args) {
+        string str = args.at(0)->get<string>();
+        string check = args.at(1)->get<string>();
+
+        return str.find(check) != std::string::npos;
+    });
+
+    env.add_callback("stringStartsWith", 2, [](Arguments& args) {
+        string str = args.at(0)->get<string>();
+        string check = args.at(1)->get<string>();
+
+        return str.find(check) == 0;
+    });
+
+    env.add_callback("stringEndsWith", 2, [](Arguments& args) {
+        string str = args.at(0)->get<string>();
+        string check = args.at(1)->get<string>();
+
+        return str.rfind(check) == (str.length() - check.length());
+    });
+
     try
     {
         env.write_with_json_file(templateFilepath, jsonfilepath, outputFilepath);