diff --git a/include/constants/form_change_types.h b/include/constants/form_change_types.h
index ac1f53bb51..74bc16cf2f 100644
--- a/include/constants/form_change_types.h
+++ b/include/constants/form_change_types.h
@@ -129,4 +129,9 @@
 // param1: tera type
 #define FORM_CHANGE_BATTLE_TERASTALLIZATION     22
 
+// Form change that activates at midnight after a certain amount of days has passed.
+// Adding this form change will automatically make the countdown start as soon the Pokémon changes into a species other than the one specified for this form change.
+// param1: amount of days
+#define FORM_CHANGE_DAYS_PASSED                 23
+
 #endif // GUARD_CONSTANTS_FORM_CHANGE_TYPES_H
diff --git a/include/pokemon.h b/include/pokemon.h
index 63a125f536..920aee7e2f 100644
--- a/include/pokemon.h
+++ b/include/pokemon.h
@@ -26,6 +26,7 @@ enum {
     MON_DATA_IS_SHINY,
     MON_DATA_HIDDEN_NATURE,
     MON_DATA_HP_LOST,
+    MON_DATA_DAYS_SINCE_FORM_CHANGE,
     MON_DATA_ENCRYPT_SEPARATOR,
     MON_DATA_NICKNAME,
     MON_DATA_NICKNAME10,
@@ -246,7 +247,8 @@ struct BoxPokemon
     u8 hasSpecies:1;
     u8 isEgg:1;
     u8 blockBoxRS:1; // Unused, but Pokémon Box Ruby & Sapphire will refuse to deposit a Pokémon with this flag set.
-    u8 unused_13:4;
+    u8 daysSinceFormChange:3; // 7 days.
+    u8 unused_13:1;
     u8 otName[PLAYER_NAME_LENGTH];
     u8 markings:4;
     u8 compressedStatus:4;
@@ -877,5 +879,7 @@ void HealPokemon(struct Pokemon *mon);
 void HealBoxPokemon(struct BoxPokemon *boxMon);
 const u8 *GetMoveName(u16 moveId);
 const u8 *GetMoveAnimationScript(u16 moveId);
+void UpdateDaysPassedSinceFormChange(u16 days);
+void TrySetDayLimitToFormChange(struct Pokemon *mon);
 
 #endif // GUARD_POKEMON_H
diff --git a/src/clock.c b/src/clock.c
index 825ccc4448..7061f96b7f 100644
--- a/src/clock.c
+++ b/src/clock.c
@@ -54,6 +54,7 @@ static void UpdatePerDay(struct Time *localTime)
         UpdateFrontierGambler(daysSince);
         SetShoalItemFlag(daysSince);
         SetRandomLotteryNumber(daysSince);
+        UpdateDaysPassedSinceFormChange(daysSince);
         *days = localTime->days;
     }
 }
diff --git a/src/data/pokemon/form_change_tables.h b/src/data/pokemon/form_change_tables.h
index 78de99f140..52f888a55b 100644
--- a/src/data/pokemon/form_change_tables.h
+++ b/src/data/pokemon/form_change_tables.h
@@ -779,6 +779,14 @@ static const struct FormChange sGreninjaBattleBondFormChangeTable[] = {
 };
 #endif //P_FAMILY_FROAKIE
 
+#if P_FAMILY_FURFROU
+static const struct FormChange sFurfrouFormChangeTable[] = {
+    {FORM_CHANGE_WITHDRAW,    SPECIES_FURFROU_NATURAL},
+    {FORM_CHANGE_DAYS_PASSED, SPECIES_FURFROU_NATURAL, 5},
+    {FORM_CHANGE_TERMINATOR},
+};
+#endif //P_FAMILY_FURFROU
+
 #if P_FAMILY_HONEDGE
 static const struct FormChange sAegislashFormChangeTable[] = {
     {FORM_CHANGE_BATTLE_SWITCH, SPECIES_AEGISLASH_SHIELD},
@@ -841,8 +849,9 @@ static const struct FormChange sDiancieFormChangeTable[] = {
 
 #if P_FAMILY_HOOPA
 static const struct FormChange sHoopaFormChangeTable[] = {
-    {FORM_CHANGE_ITEM_USE, SPECIES_HOOPA_UNBOUND, ITEM_PRISON_BOTTLE, SPECIES_HOOPA_CONFINED},
-    {FORM_CHANGE_WITHDRAW, SPECIES_HOOPA_CONFINED},
+    {FORM_CHANGE_ITEM_USE,    SPECIES_HOOPA_UNBOUND, ITEM_PRISON_BOTTLE, SPECIES_HOOPA_CONFINED},
+    {FORM_CHANGE_WITHDRAW,    SPECIES_HOOPA_CONFINED},
+    {FORM_CHANGE_DAYS_PASSED, SPECIES_HOOPA_CONFINED, 3},
     {FORM_CHANGE_TERMINATOR},
 };
 #endif //P_FAMILY_HOOPA
diff --git a/src/data/pokemon/species_info/gen_6_families.h b/src/data/pokemon/species_info/gen_6_families.h
index 09ad2a01d0..46c776639c 100644
--- a/src/data/pokemon/species_info/gen_6_families.h
+++ b/src/data/pokemon/species_info/gen_6_families.h
@@ -2156,6 +2156,7 @@ const struct SpeciesInfo gSpeciesInfoGen6[] =
         .teachableLearnset = sFurfrouTeachableLearnset,                                                 \
         .eggMoveLearnset = sFurfrouEggMoveLearnset,                                                     \
         .formSpeciesIdTable = sFurfrouFormSpeciesIdTable,                                               \
+        .formChangeTable = sFurfrouFormChangeTable,                                                     \
     }
 
     [SPECIES_FURFROU_NATURAL] =        FURFROU_MISC_INFO(Natural,       FALSE, 48, 3, 56, 0, 0),
diff --git a/src/party_menu.c b/src/party_menu.c
index 2b80361141..c46c74393f 100644
--- a/src/party_menu.c
+++ b/src/party_menu.c
@@ -6361,6 +6361,7 @@ static void Task_TryItemUseFormChange(u8 taskId)
     case 0:
         targetSpecies = gTasks[taskId].tTargetSpecies;
         SetMonData(mon, MON_DATA_SPECIES, &targetSpecies);
+        TrySetDayLimitToFormChange(mon);
         CalculateMonStats(mon);
         gTasks[taskId].tState++;
         break;
diff --git a/src/pokemon.c b/src/pokemon.c
index 8c6a5fcce6..19394b8dfd 100644
--- a/src/pokemon.c
+++ b/src/pokemon.c
@@ -2856,6 +2856,9 @@ u32 GetBoxMonData3(struct BoxPokemon *boxMon, s32 field, u8 *data)
             retVal = nature ^ boxMon->hiddenNatureModifier;
             break;
         }
+        case MON_DATA_DAYS_SINCE_FORM_CHANGE:
+            retVal = boxMon->daysSinceFormChange;
+            break;
         default:
             break;
         }
@@ -3290,6 +3293,9 @@ void SetBoxMonData(struct BoxPokemon *boxMon, s32 field, const void *dataArg)
             boxMon->hiddenNatureModifier = nature ^ hiddenNature;
             break;
         }
+        case MON_DATA_DAYS_SINCE_FORM_CHANGE:
+            SET8(boxMon->daysSinceFormChange);
+            break;
         }
     }
 
@@ -6523,6 +6529,7 @@ u16 GetFormChangeTargetSpeciesBoxMon(struct BoxPokemon *boxMon, u16 method, u32
                     break;
                 case FORM_CHANGE_WITHDRAW:
                 case FORM_CHANGE_FAINT:
+                case FORM_CHANGE_DAYS_PASSED:
                     targetSpecies = formChanges[i].targetSpecies;
                     break;
                 case FORM_CHANGE_STATUS:
@@ -6550,6 +6557,22 @@ u16 GetFormChangeTargetSpeciesBoxMon(struct BoxPokemon *boxMon, u16 method, u32
     return targetSpecies;
 }
 
+void TrySetDayLimitToFormChange(struct Pokemon *mon)
+{
+    u32 i;
+    u16 species = GetMonData(mon, MON_DATA_SPECIES, NULL);
+    const struct FormChange *formChanges = GetSpeciesFormChanges(species);
+
+    for (i = 0; formChanges[i].method != FORM_CHANGE_TERMINATOR; i++)
+    {
+        if (formChanges[i].method == FORM_CHANGE_DAYS_PASSED && species != formChanges[i].targetSpecies)
+        {
+            SetMonData(mon, MON_DATA_DAYS_SINCE_FORM_CHANGE, &formChanges[i].param1);
+            break;
+        }
+    }
+}
+
 bool32 DoesSpeciesHaveFormChangeMethod(u16 species, u16 method)
 {
     u32 i;
@@ -6866,3 +6889,38 @@ const u8 *GetMoveAnimationScript(u16 moveId)
     }
     return gMovesInfo[moveId].battleAnimScript;
 }
+
+void UpdateDaysPassedSinceFormChange(u16 days)
+{
+    u32 i;
+    for (i = 0; i < PARTY_SIZE; i++)
+    {
+        struct Pokemon *mon = &gPlayerParty[i];
+        u8 daysSinceFormChange;
+
+        if (!GetMonData(mon, MON_DATA_SPECIES, 0))
+            continue;
+
+        daysSinceFormChange = GetMonData(mon, MON_DATA_DAYS_SINCE_FORM_CHANGE, 0);
+        if (daysSinceFormChange == 0)
+            continue;
+
+        if (daysSinceFormChange > days)
+            daysSinceFormChange -= days;
+        else
+            daysSinceFormChange = 0;
+
+        SetMonData(mon, MON_DATA_DAYS_SINCE_FORM_CHANGE, &daysSinceFormChange);
+
+        if (daysSinceFormChange == 0)
+        {
+            u16 targetSpecies = GetFormChangeTargetSpecies(mon, FORM_CHANGE_DAYS_PASSED, 0);
+            
+            if (targetSpecies != SPECIES_NONE)
+            {
+                SetMonData(mon, MON_DATA_SPECIES, &targetSpecies);
+                CalculateMonStats(mon);
+            }
+        }
+    }
+}