diff --git a/onchain/src/art_peace.cairo b/onchain/src/art_peace.cairo
index 11f79653..288604f8 100644
--- a/onchain/src/art_peace.cairo
+++ b/onchain/src/art_peace.cairo
@@ -29,6 +29,7 @@ pub mod ArtPeace {
         creation_time: u64,
         end_time: u64,
         day_index: u32,
+        start_day_time: u64,
         // Map: (day_index, quest_id) -> quest contract address
         daily_quests: LegacyMap::<(u32, u32), ContractAddress>,
         main_quests_count: u32,
@@ -43,11 +44,18 @@ pub mod ArtPeace {
     #[event]
     #[derive(Drop, starknet::Event)]
     enum Event {
+        Newday: NewDay,
         PixelPlaced: PixelPlaced,
         #[flat]
         TemplateEvent: TemplateStoreComponent::Event,
     }
 
+    #[derive(Drop, starknet::Event)]
+    struct NewDay {
+        #[key]
+        day_index: u32,
+    }
+
     #[derive(Drop, starknet::Event)]
     struct PixelPlaced {
         #[key]
@@ -71,6 +79,8 @@ pub mod ArtPeace {
         pub main_quests: Span<ContractAddress>,
     }
 
+    const DAY_IN_SECONDS: u64 = consteval_int!(60 * 60 * 24);
+
     #[constructor]
     fn constructor(ref self: ContractState, init_params: InitParams) {
         self.canvas_width.write(init_params.canvas_width);
@@ -88,6 +98,7 @@ pub mod ArtPeace {
         };
 
         self.creation_time.write(starknet::get_block_timestamp());
+        self.start_day_time.write(starknet::get_block_timestamp());
         self.end_time.write(init_params.end_time);
         self.day_index.write(0);
 
@@ -246,6 +257,17 @@ pub mod ArtPeace {
             self.day_index.read()
         }
 
+        fn increase_day_index(ref self: ContractState) {
+            let block_timestamp = starknet::get_block_timestamp();
+            let start_day_time = self.start_day_time.read();
+
+            assert(block_timestamp >= start_day_time + DAY_IN_SECONDS, 'day has not passed');
+
+            self.day_index.write(self.day_index.read() + 1);
+            self.start_day_time.write(block_timestamp);
+            self.emit(NewDay { day_index: self.day_index.read() });
+        }
+
         fn get_daily_quest_count(self: @ContractState) -> core::zeroable::NonZero::<u32> {
             // TODO: hardcoded 3 daily quests
             3
@@ -425,3 +447,4 @@ pub mod ArtPeace {
         }
     }
 }
+
diff --git a/onchain/src/interface.cairo b/onchain/src/interface.cairo
index 5d1b785a..9882ff36 100644
--- a/onchain/src/interface.cairo
+++ b/onchain/src/interface.cairo
@@ -40,6 +40,9 @@ pub trait IArtPeace<TContractState> {
     fn get_end_time(self: @TContractState) -> u64;
     fn get_day(self: @TContractState) -> u32;
 
+    // Start a new day
+    fn increase_day_index(ref self: TContractState);
+
     // Get quest info
     fn get_daily_quest_count(self: @TContractState) -> core::zeroable::NonZero::<u32>;
     fn get_daily_quest(
diff --git a/onchain/src/tests/art_peace.cairo b/onchain/src/tests/art_peace.cairo
index ce0fa0a9..eff84e67 100644
--- a/onchain/src/tests/art_peace.cairo
+++ b/onchain/src/tests/art_peace.cairo
@@ -5,10 +5,14 @@ use art_peace::templates::{
     ITemplateVerifierDispatcherTrait, TemplateMetadata
 };
 
+use core::poseidon::PoseidonTrait;
+use core::hash::{HashStateTrait, HashStateExTrait};
+
 use snforge_std as snf;
 use snforge_std::{CheatTarget, ContractClassTrait};
 use starknet::{ContractAddress, contract_address_const};
 
+const DAY_IN_SECONDS: u64 = consteval_int!(60 * 60 * 24);
 const WIDTH: u128 = 100;
 const HEIGHT: u128 = 100;
 const TIME_BETWEEN_PIXELS: u64 = 10;
@@ -98,6 +102,21 @@ fn warp_to_next_available_time(art_peace: IArtPeaceDispatcher) {
     snf::start_warp(CheatTarget::One(art_peace.contract_address), last_time + TIME_BETWEEN_PIXELS);
 }
 
+fn compute_template_hash(template: Span<u8>) -> felt252 {
+    let template_len = template.len();
+    if template_len == 0 {
+        return 0;
+    }
+
+    let mut hasher = PoseidonTrait::new();
+    let mut i = 0;
+    while i < template_len {
+        hasher = hasher.update_with(*template.at(i));
+        i += 1;
+    };
+    hasher.finalize()
+}
+
 #[test]
 fn deploy_test() {
     let art_peace = IArtPeaceDispatcher { contract_address: deploy_contract() };
@@ -212,25 +231,6 @@ fn pixel_quest_test() {
     );
 }
 
-use core::poseidon::PoseidonTrait;
-use core::hash::{HashStateTrait, HashStateExTrait};
-
-// TODO: Move to src
-fn compute_template_hash(template: Span<u8>) -> felt252 {
-    let template_len = template.len();
-    if template_len == 0 {
-        return 0;
-    }
-
-    let mut hasher = PoseidonTrait::new();
-    let mut i = 0;
-    while i < template_len {
-        hasher = hasher.update_with(*template.at(i));
-        i += 1;
-    };
-    hasher.finalize()
-}
-
 #[test]
 fn template_full_basic_test() {
     let art_peace = IArtPeaceDispatcher { contract_address: deploy_contract() };
@@ -310,6 +310,34 @@ fn template_full_basic_test() {
         "Template is not completed after it should be"
     );
 }
+
+#[test]
+fn increase_day_test() {
+    let art_peace_address = deploy_contract();
+    let art_peace = IArtPeaceDispatcher { contract_address: art_peace_address };
+
+    let current_day_index = art_peace.get_day();
+    assert!(current_day_index == 0, "day index wrongly initialized");
+
+    snf::start_warp(CheatTarget::One(art_peace_address), DAY_IN_SECONDS);
+    art_peace.increase_day_index();
+    let current_day_index = art_peace.get_day();
+    assert!(current_day_index == 1, "day index not updated");
+    snf::stop_warp(CheatTarget::One(art_peace_address));
+}
+
+#[test]
+#[should_panic(expected: ('day has not passed',))]
+fn increase_day_panic_test() {
+    let art_peace_address = deploy_contract();
+    let art_peace = IArtPeaceDispatcher { contract_address: art_peace_address };
+
+    let current_day_index = art_peace.get_day();
+    assert!(current_day_index == 0, "day index wrongly initialized");
+
+    snf::start_warp(CheatTarget::One(art_peace_address), DAY_IN_SECONDS - 1);
+    art_peace.increase_day_index();
+}
 // TODO: test invalid template inputs