diff --git a/common/aclock/aclock.go b/common/aclock/aclock.go
new file mode 100644
index 0000000000..608941027d
--- /dev/null
+++ b/common/aclock/aclock.go
@@ -0,0 +1,50 @@
+// Copyright 2018 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+// Package aclock contains an adjustable clock implementation. The time can be
+// adjusted by adding an offset.
+package aclock
+
+import (
+	"errors"
+	"time"
+)
+
+var offset time.Duration
+
+// AddOffset adds offset d to the current offset. d cannot be negative, and an
+// error will be returned if the resulting offset overflows time.Duration.
+func AddOffset(d time.Duration) (time.Duration, error) {
+	if d < 0 {
+		return 0, errors.New("aclock: duration for offset cannot be negative")
+	}
+	if offset+d < offset {
+		return 0, errors.New("aclock: offset overflow")
+	}
+	offset += d
+	return offset, nil
+}
+
+// Now returns the current time with the offset applied.
+func Now() time.Time {
+	return time.Now().Add(offset)
+}
+
+// NowWithOffset returns the current time with the offset applied and the offset
+// itself.
+func NowWithOffset() (time.Time, time.Duration) {
+	return time.Now().Add(offset), offset
+}
diff --git a/consensus/clique/clique.go b/consensus/clique/clique.go
index c79c30caed..3d293d042f 100644
--- a/consensus/clique/clique.go
+++ b/consensus/clique/clique.go
@@ -27,6 +27,7 @@ import (
 
 	"github.com/ethereum/go-ethereum/accounts"
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/common/aclock"
 	"github.com/ethereum/go-ethereum/common/hexutil"
 	"github.com/ethereum/go-ethereum/consensus"
 	"github.com/ethereum/go-ethereum/consensus/misc"
@@ -279,7 +280,7 @@ func (c *Clique) verifyHeader(chain consensus.ChainReader, header *types.Header,
 	number := header.Number.Uint64()
 
 	// Don't waste time checking blocks from the future
-	if header.Time.Cmp(big.NewInt(time.Now().Unix())) > 0 {
+	if header.Time.Cmp(big.NewInt(aclock.Now().Unix())) > 0 {
 		return consensus.ErrFutureBlock
 	}
 	// Checkpoint blocks need to enforce zero beneficiary
@@ -571,8 +572,8 @@ func (c *Clique) Prepare(chain consensus.ChainReader, header *types.Header) erro
 		return consensus.ErrUnknownAncestor
 	}
 	header.Time = new(big.Int).Add(parent.Time, new(big.Int).SetUint64(c.config.Period))
-	if header.Time.Int64() < time.Now().Unix() {
-		header.Time = big.NewInt(time.Now().Unix())
+	if header.Time.Int64() < aclock.Now().Unix() {
+		header.Time = big.NewInt(aclock.Now().Unix())
 	}
 	return nil
 }
@@ -637,7 +638,7 @@ func (c *Clique) Seal(chain consensus.ChainReader, block *types.Block, results c
 		}
 	}
 	// Sweet, the protocol permits us to sign the block, wait for our time
-	delay := time.Unix(header.Time.Int64(), 0).Sub(time.Now()) // nolint: gosimple
+	delay := time.Unix(header.Time.Int64(), 0).Sub(aclock.Now()) // nolint: gosimple
 	if header.Difficulty.Cmp(diffNoTurn) == 0 {
 		// It's not our turn explicitly to sign, delay it a bit
 		wiggle := time.Duration(len(snap.Signers)/2+1) * wiggleTime
diff --git a/core/blockchain.go b/core/blockchain.go
index 156efe303a..6d555b9bc9 100644
--- a/core/blockchain.go
+++ b/core/blockchain.go
@@ -43,7 +43,7 @@ import (
 	"github.com/ethereum/go-ethereum/params"
 	"github.com/ethereum/go-ethereum/rlp"
 	"github.com/ethereum/go-ethereum/trie"
-	"github.com/hashicorp/golang-lru"
+	lru "github.com/hashicorp/golang-lru"
 )
 
 var (
diff --git a/internal/ethapi/api.go b/internal/ethapi/api.go
index 26dc1e8a01..11b25ebfac 100644
--- a/internal/ethapi/api.go
+++ b/internal/ethapi/api.go
@@ -29,6 +29,7 @@ import (
 	"github.com/ethereum/go-ethereum/accounts"
 	"github.com/ethereum/go-ethereum/accounts/keystore"
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/common/aclock"
 	"github.com/ethereum/go-ethereum/common/hexutil"
 	"github.com/ethereum/go-ethereum/common/math"
 	"github.com/ethereum/go-ethereum/consensus/ethash"
@@ -1562,6 +1563,16 @@ func (api *PrivateDebugAPI) SetHead(number hexutil.Uint64) {
 	api.b.SetHead(uint64(number))
 }
 
+// IncreaseTime increase the time offset for the clock used in consensus and
+// mining. It has the effect of changing the timestamp of the next mined block.
+func (api *PrivateDebugAPI) IncreaseTime(seconds uint64) (uint64, error) {
+	offset, err := aclock.AddOffset(time.Duration(seconds) * time.Second)
+	if err != nil {
+		return 0, err
+	}
+	return uint64(offset.Seconds()), nil
+}
+
 // PublicNetAPI offers network related RPC methods
 type PublicNetAPI struct {
 	net            *p2p.Server
diff --git a/internal/web3ext/web3ext.go b/internal/web3ext/web3ext.go
index 6b98c8b7e1..299002b6bc 100644
--- a/internal/web3ext/web3ext.go
+++ b/internal/web3ext/web3ext.go
@@ -236,6 +236,11 @@ web3._extend({
 			call: 'debug_setHead',
 			params: 1
 		}),
+		new web3._extend.Method({
+			name: 'increaseTime',
+			call: 'debug_increaseTime',
+			params: 1
+		}),
 		new web3._extend.Method({
 			name: 'seedHash',
 			call: 'debug_seedHash',
diff --git a/miner/worker.go b/miner/worker.go
index 48473796bc..63e698e605 100644
--- a/miner/worker.go
+++ b/miner/worker.go
@@ -26,6 +26,7 @@ import (
 
 	mapset "github.com/deckarep/golang-set"
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/common/aclock"
 	"github.com/ethereum/go-ethereum/consensus"
 	"github.com/ethereum/go-ethereum/consensus/misc"
 	"github.com/ethereum/go-ethereum/core"
@@ -820,15 +821,19 @@ func (w *worker) commitNewWork(interrupt *int32, noempty bool, timestamp int64)
 	w.mu.RLock()
 	defer w.mu.RUnlock()
 
-	tstart := time.Now()
+	tstart, startOffset := aclock.NowWithOffset()
 	parent := w.chain.CurrentBlock()
 
 	if parent.Time().Cmp(new(big.Int).SetInt64(timestamp)) >= 0 {
 		timestamp = parent.Time().Int64() + 1
 	}
 	// this will ensure we're not going off too far in the future
-	if now := time.Now().Unix(); timestamp > now+1 {
-		wait := time.Duration(timestamp-now) * time.Second
+	now, nowOffset := aclock.NowWithOffset()
+	// nowWithOffset accounts for differences between the current aclock offset
+	// the offset when the current block was mined.
+	nowWithOffset := now.Unix() + int64(nowOffset.Seconds()-startOffset.Seconds())
+	if timestamp > nowWithOffset+1 {
+		wait := time.Duration(timestamp-nowWithOffset) * time.Second
 		log.Info("Mining too far in the future", "wait", common.PrettyDuration(wait))
 		time.Sleep(wait)
 	}