diff --git a/Blockchain/Sources/Blockchain/Blockchain.swift b/Blockchain/Sources/Blockchain/Blockchain.swift
index 0892785a..4bf85000 100644
--- a/Blockchain/Sources/Blockchain/Blockchain.swift
+++ b/Blockchain/Sources/Blockchain/Blockchain.swift
@@ -9,10 +9,12 @@ public final class Blockchain: Sendable {
     public let config: ProtocolConfigRef
 
     private let dataProvider: BlockchainDataProvider
+    private let timeProvider: TimeProvider
 
-    public init(config: ProtocolConfigRef, dataProvider: BlockchainDataProvider) async {
+    public init(config: ProtocolConfigRef, dataProvider: BlockchainDataProvider, timeProvider: TimeProvider) async {
         self.config = config
         self.dataProvider = dataProvider
+        self.timeProvider = timeProvider
     }
 
     public func importBlock(_ block: BlockRef) async throws {
@@ -21,7 +23,8 @@ public final class Blockchain: Sendable {
 
             let runtime = Runtime(config: config)
             let parent = try await dataProvider.getState(hash: block.header.parentHash)
-            let state = try runtime.apply(block: block, state: parent)
+            let timeslot = timeProvider.getTime() / UInt32(config.value.slotPeriodSeconds)
+            let state = try runtime.apply(block: block, state: parent, context: .init(timeslot: timeslot))
             try await dataProvider.add(state: state)
         }
     }
diff --git a/Blockchain/Sources/Blockchain/Runtime.swift b/Blockchain/Sources/Blockchain/Runtime.swift
index a5397147..90e73244 100644
--- a/Blockchain/Sources/Blockchain/Runtime.swift
+++ b/Blockchain/Sources/Blockchain/Runtime.swift
@@ -5,6 +5,15 @@ public final class Runtime {
     public enum Error: Swift.Error {
         case safroleError(SafroleError)
         case invalidValidatorEd25519Key
+        case invalidTimeslot
+    }
+
+    public struct ApplyContext {
+        public let timeslot: TimeslotIndex
+
+        public init(timeslot: TimeslotIndex) {
+            self.timeslot = timeslot
+        }
     }
 
     public let config: ProtocolConfigRef
@@ -13,7 +22,18 @@ public final class Runtime {
         self.config = config
     }
 
-    public func apply(block: BlockRef, state prevState: StateRef) throws(Error) -> StateRef {
+    public func validate(block: BlockRef, state _: StateRef, context: ApplyContext) throws(Error) {
+        guard context.timeslot >= block.header.timeslotIndex else {
+            throw Error.invalidTimeslot
+        }
+
+        // TODO: validate block.header.seal
+        // TODO: abstract input validation logic from Safrole state update function and call it here
+    }
+
+    public func apply(block: BlockRef, state prevState: StateRef, context: ApplyContext) throws(Error) -> StateRef {
+        try validate(block: block, state: prevState, context: context)
+
         var newState = prevState.value
         newState.lastBlock = block
 
diff --git a/Blockchain/Sources/Blockchain/TimeProvider.swift b/Blockchain/Sources/Blockchain/TimeProvider.swift
new file mode 100644
index 00000000..6279a5a8
--- /dev/null
+++ b/Blockchain/Sources/Blockchain/TimeProvider.swift
@@ -0,0 +1,35 @@
+import Foundation
+
+public protocol TimeProvider: Sendable {
+    func getTime() -> UInt32
+}
+
+public struct SystemTimeProvider: TimeProvider {
+    public init() {}
+
+    public func getTime() -> UInt32 {
+        Date().timeIntervalSinceJamCommonEra
+    }
+}
+
+public struct FixedTimeProvider: TimeProvider {
+    private let time: UInt32
+
+    public init(time: UInt32) {
+        self.time = time
+    }
+
+    public func getTime() -> UInt32 {
+        time
+    }
+}
+
+extension Date {
+    public var timeIntervalSinceJamCommonEra: UInt32 {
+        // the Jam Common Era: 1200 UTC on January 1, 2024
+        // number of seconds since the Unix epoch
+        let beginning = 1_704_110_400.0
+        let now = timeIntervalSince1970
+        return UInt32(now - beginning)
+    }
+}
diff --git a/Node/Sources/Node/Node.swift b/Node/Sources/Node/Node.swift
index 9dee611b..9b2d5465 100644
--- a/Node/Sources/Node/Node.swift
+++ b/Node/Sources/Node/Node.swift
@@ -25,7 +25,8 @@ public class Node {
 
         let genesisState = try genesis.toState(config: config.protcol)
         let dataProvider = await InMemoryDataProvider(genesis: genesisState)
-        blockchain = await Blockchain(config: config.protcol, dataProvider: dataProvider)
+        let timeProvider = SystemTimeProvider()
+        blockchain = await Blockchain(config: config.protcol, dataProvider: dataProvider, timeProvider: timeProvider)
 
         rpcServer = try Server(config: config.rpc, source: blockchain)
     }