diff --git a/src/query/api/v1/handler/prometheus/common.go b/src/query/api/v1/handler/prometheus/common.go
index ded4732681..87859f9caf 100644
--- a/src/query/api/v1/handler/prometheus/common.go
+++ b/src/query/api/v1/handler/prometheus/common.go
@@ -176,6 +176,35 @@ func parseTagCompletionQueries(r *http.Request) ([]string, error) {
 	return queries, nil
 }
 
+// ParseStartAndEnd parses start and end params from the request.
+func ParseStartAndEnd(
+	r *http.Request,
+	parseOpts xpromql.ParseOptions,
+) (time.Time, time.Time, error) {
+	if err := r.ParseForm(); err != nil {
+		return time.Time{}, time.Time{}, xerrors.NewInvalidParamsError(err)
+	}
+
+	start, err := util.ParseTimeStringWithDefault(r.FormValue("start"),
+		time.Unix(0, 0))
+	if err != nil {
+		return time.Time{}, time.Time{}, xerrors.NewInvalidParamsError(err)
+	}
+
+	end, err := util.ParseTimeStringWithDefault(r.FormValue("end"),
+		parseOpts.NowFn()())
+	if err != nil {
+		return time.Time{}, time.Time{}, xerrors.NewInvalidParamsError(err)
+	}
+
+	if start.After(end) {
+		err := fmt.Errorf("start %v must be after end %v", start, end)
+		return time.Time{}, time.Time{}, xerrors.NewInvalidParamsError(err)
+	}
+
+	return start, end, nil
+}
+
 // ParseSeriesMatchQuery parses all params from the GET request.
 func ParseSeriesMatchQuery(
 	r *http.Request,
@@ -188,16 +217,9 @@ func ParseSeriesMatchQuery(
 		return nil, xerrors.NewInvalidParamsError(errors.ErrInvalidMatchers)
 	}
 
-	start, err := util.ParseTimeStringWithDefault(r.FormValue("start"),
-		time.Unix(0, 0))
-	if err != nil {
-		return nil, xerrors.NewInvalidParamsError(err)
-	}
-
-	end, err := util.ParseTimeStringWithDefault(r.FormValue("end"),
-		time.Now())
+	start, end, err := ParseStartAndEnd(r, parseOpts)
 	if err != nil {
-		return nil, xerrors.NewInvalidParamsError(err)
+		return nil, err
 	}
 
 	queries := make([]*storage.FetchQuery, len(matcherValues))
diff --git a/src/query/api/v1/handler/prometheus/common_test.go b/src/query/api/v1/handler/prometheus/common_test.go
index 7e7e0d091d..b8479ae4ab 100644
--- a/src/query/api/v1/handler/prometheus/common_test.go
+++ b/src/query/api/v1/handler/prometheus/common_test.go
@@ -22,16 +22,22 @@ package prometheus
 
 import (
 	"bytes"
+	"context"
 	"fmt"
+	"net/http"
 	"net/http/httptest"
 	"strings"
 	"testing"
+	"time"
 
 	"github.com/m3db/m3/src/query/models"
+	"github.com/m3db/m3/src/query/parser/promql"
 	"github.com/m3db/m3/src/query/test"
 	xerrors "github.com/m3db/m3/src/x/errors"
+	xhttp "github.com/m3db/m3/src/x/net/http"
 
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 func TestPromCompressedReadSuccess(t *testing.T) {
@@ -102,7 +108,7 @@ func TestRenderSeriesMatchResultsNoTags(t *testing.T) {
 	}
 
 	seriesMatchResult := []models.Metrics{
-		models.Metrics{
+		{
 			toTags("name", tag{name: "a", value: "b"}, tag{name: "role", value: "appears"}),
 			toTags("name2", tag{name: "c", value: "d"}, tag{name: "e", value: "f"}),
 		},
@@ -135,3 +141,55 @@ func TestRenderSeriesMatchResultsNoTags(t *testing.T) {
 		assert.Equal(t, expected, w.value)
 	}
 }
+
+func TestParseStartAndEnd(t *testing.T) {
+	endTime := time.Now().Truncate(time.Hour)
+	opts := promql.NewParseOptions().SetNowFn(func() time.Time { return endTime })
+
+	tests := []struct {
+		querystring string
+		exStart     time.Time
+		exEnd       time.Time
+		exErr       bool
+	}{
+		{querystring: "", exStart: time.Unix(0, 0), exEnd: endTime},
+		{querystring: "start=100", exStart: time.Unix(100, 0), exEnd: endTime},
+		{querystring: "start=100&end=200", exStart: time.Unix(100, 0), exEnd: time.Unix(200, 0)},
+		{querystring: "start=200&end=100", exErr: true},
+		{querystring: "start=foo&end=100", exErr: true},
+		{querystring: "start=100&end=bar", exErr: true},
+	}
+
+	for _, tt := range tests {
+		t.Run(fmt.Sprintf("GET_%s", tt.querystring), func(t *testing.T) {
+			req, err := http.NewRequestWithContext(context.Background(), http.MethodGet,
+				fmt.Sprintf("/?%s", tt.querystring), nil)
+			require.NoError(t, err)
+
+			start, end, err := ParseStartAndEnd(req, opts)
+			if tt.exErr {
+				require.Error(t, err)
+			} else {
+				assert.Equal(t, tt.exStart, start)
+				assert.Equal(t, tt.exEnd, end)
+			}
+		})
+	}
+
+	for _, tt := range tests {
+		t.Run(fmt.Sprintf("POST_%s", tt.querystring), func(t *testing.T) {
+			b := bytes.NewBuffer([]byte(tt.querystring))
+			req, err := http.NewRequestWithContext(context.Background(), http.MethodPost, "/", b)
+			require.NoError(t, err)
+			req.Header.Add(xhttp.HeaderContentType, xhttp.ContentTypeFormURLEncoded)
+
+			start, end, err := ParseStartAndEnd(req, opts)
+			if tt.exErr {
+				require.Error(t, err)
+			} else {
+				assert.Equal(t, tt.exStart, start)
+				assert.Equal(t, tt.exEnd, end)
+			}
+		})
+	}
+}
diff --git a/src/query/api/v1/handler/prometheus/native/list_tags.go b/src/query/api/v1/handler/prometheus/native/list_tags.go
index 7841a0dca7..23aa9268c8 100644
--- a/src/query/api/v1/handler/prometheus/native/list_tags.go
+++ b/src/query/api/v1/handler/prometheus/native/list_tags.go
@@ -23,16 +23,15 @@ package native
 import (
 	"context"
 	"net/http"
-	"time"
 
 	"github.com/m3db/m3/src/query/api/v1/handler"
 	"github.com/m3db/m3/src/query/api/v1/handler/prometheus"
 	"github.com/m3db/m3/src/query/api/v1/handler/prometheus/handleroptions"
 	"github.com/m3db/m3/src/query/api/v1/options"
 	"github.com/m3db/m3/src/query/models"
+	"github.com/m3db/m3/src/query/parser/promql"
 	"github.com/m3db/m3/src/query/storage"
 	"github.com/m3db/m3/src/query/util/logging"
-	"github.com/m3db/m3/src/x/clock"
 	"github.com/m3db/m3/src/x/instrument"
 	xhttp "github.com/m3db/m3/src/x/net/http"
 
@@ -53,7 +52,7 @@ var (
 type ListTagsHandler struct {
 	storage             storage.Storage
 	fetchOptionsBuilder handleroptions.FetchOptionsBuilder
-	nowFn               clock.NowFn
+	parseOpts           promql.ParseOptions
 	instrumentOpts      instrument.Options
 }
 
@@ -62,7 +61,7 @@ func NewListTagsHandler(opts options.HandlerOptions) http.Handler {
 	return &ListTagsHandler{
 		storage:             opts.Storage(),
 		fetchOptionsBuilder: opts.FetchOptionsBuilder(),
-		nowFn:               opts.NowFn(),
+		parseOpts:           promql.NewParseOptions().SetNowFn(opts.NowFn()),
 		instrumentOpts:      opts.InstrumentOpts(),
 	}
 }
@@ -72,13 +71,17 @@ func (h *ListTagsHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	logger := logging.WithContext(ctx, h.instrumentOpts)
 	w.Header().Set(xhttp.HeaderContentType, xhttp.ContentTypeJSON)
 
+	start, end, err := prometheus.ParseStartAndEnd(r, h.parseOpts)
+	if err != nil {
+		xhttp.WriteError(w, err)
+		return
+	}
+
 	query := &storage.CompleteTagsQuery{
 		CompleteNameOnly: true,
 		TagMatchers:      models.Matchers{{Type: models.MatchAll}},
-
-		// NB: necessarily spans entire possible query range.
-		Start: time.Time{},
-		End:   h.nowFn(),
+		Start:            start,
+		End:              end,
 	}
 
 	opts, rErr := h.fetchOptionsBuilder.NewFetchOptions(r)
diff --git a/src/query/api/v1/handler/prometheus/native/list_tags_test.go b/src/query/api/v1/handler/prometheus/native/list_tags_test.go
index f33ef27b18..f0e2e24c4b 100644
--- a/src/query/api/v1/handler/prometheus/native/list_tags_test.go
+++ b/src/query/api/v1/handler/prometheus/native/list_tags_test.go
@@ -42,7 +42,7 @@ import (
 )
 
 type listTagsMatcher struct {
-	now time.Time
+	start, end time.Time
 }
 
 func (m *listTagsMatcher) String() string { return "list tags query" }
@@ -52,12 +52,12 @@ func (m *listTagsMatcher) Matches(x interface{}) bool {
 		return false
 	}
 
-	if !q.Start.Equal(time.Time{}) {
+	if !q.Start.Equal(m.start) {
 		return false
 	}
 
 	// NB: end time for the query should be roughly `Now`
-	if !q.End.Equal(m.now) {
+	if !q.End.Equal(m.end) {
 		return false
 	}
 
@@ -119,7 +119,7 @@ func testListTags(t *testing.T, meta block.ResultMetadata, header string) {
 		SetNowFn(nowFn)
 	h := NewListTagsHandler(opts)
 	for _, method := range []string{"GET", "POST"} {
-		matcher := &listTagsMatcher{now: now}
+		matcher := &listTagsMatcher{start: time.Unix(0, 0), end: now}
 		store.EXPECT().CompleteTags(gomock.Any(), matcher, gomock.Any()).
 			Return(storeResult, nil)
 
@@ -150,25 +150,19 @@ func TestListErrorTags(t *testing.T) {
 
 	// setup storage and handler
 	store := storage.NewMockStorage(ctrl)
-	now := time.Now()
-	nowFn := func() time.Time {
-		return now
-	}
-
 	fb, err := handleroptions.NewFetchOptionsBuilder(
 		handleroptions.FetchOptionsBuilderOptions{Timeout: 15 * time.Second})
 	require.NoError(t, err)
 	opts := options.EmptyHandlerOptions().
 		SetStorage(store).
-		SetFetchOptionsBuilder(fb).
-		SetNowFn(nowFn)
+		SetFetchOptionsBuilder(fb)
 	handler := NewListTagsHandler(opts)
 	for _, method := range []string{"GET", "POST"} {
-		matcher := &listTagsMatcher{now: now}
+		matcher := &listTagsMatcher{start: time.Unix(100, 0), end: time.Unix(1000, 0)}
 		store.EXPECT().CompleteTags(gomock.Any(), matcher, gomock.Any()).
 			Return(nil, errors.New("err"))
 
-		req := httptest.NewRequest(method, "/labels", nil)
+		req := httptest.NewRequest(method, "/labels?start=100&end=1000", nil)
 		w := httptest.NewRecorder()
 
 		handler.ServeHTTP(w, req)
diff --git a/src/query/api/v1/handler/prometheus/remote/tag_values.go b/src/query/api/v1/handler/prometheus/remote/tag_values.go
index f146ffb649..61c5935130 100644
--- a/src/query/api/v1/handler/prometheus/remote/tag_values.go
+++ b/src/query/api/v1/handler/prometheus/remote/tag_values.go
@@ -23,7 +23,6 @@ package remote
 import (
 	"context"
 	"net/http"
-	"time"
 
 	"github.com/m3db/m3/src/query/api/v1/handler"
 	"github.com/m3db/m3/src/query/api/v1/handler/prometheus"
@@ -31,10 +30,10 @@ import (
 	"github.com/m3db/m3/src/query/api/v1/options"
 	"github.com/m3db/m3/src/query/errors"
 	"github.com/m3db/m3/src/query/models"
+	"github.com/m3db/m3/src/query/parser/promql"
 	"github.com/m3db/m3/src/query/storage"
 	"github.com/m3db/m3/src/query/storage/m3/consolidators"
 	"github.com/m3db/m3/src/query/util/logging"
-	"github.com/m3db/m3/src/x/clock"
 	"github.com/m3db/m3/src/x/instrument"
 	xhttp "github.com/m3db/m3/src/x/net/http"
 
@@ -58,7 +57,7 @@ const (
 type TagValuesHandler struct {
 	storage             storage.Storage
 	fetchOptionsBuilder handleroptions.FetchOptionsBuilder
-	nowFn               clock.NowFn
+	parseOpts           promql.ParseOptions
 	instrumentOpts      instrument.Options
 }
 
@@ -72,7 +71,7 @@ func NewTagValuesHandler(options options.HandlerOptions) http.Handler {
 	return &TagValuesHandler{
 		storage:             options.Storage(),
 		fetchOptionsBuilder: options.FetchOptionsBuilder(),
-		nowFn:               options.NowFn(),
+		parseOpts:           promql.NewParseOptions().SetNowFn(options.NowFn()),
 		instrumentOpts:      options.InstrumentOpts(),
 	}
 }
@@ -85,7 +84,7 @@ func (h *TagValuesHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	query, err := h.parseTagValuesToQuery(r)
 	if err != nil {
 		logger.Error("unable to parse tag values to query", zap.Error(err))
-		xhttp.WriteError(w, xhttp.NewError(err, http.StatusBadRequest))
+		xhttp.WriteError(w, err)
 		return
 	}
 
@@ -117,14 +116,18 @@ func (h *TagValuesHandler) parseTagValuesToQuery(
 	vars := mux.Vars(r)
 	name, ok := vars[NameReplace]
 	if !ok || len(name) == 0 {
-		return nil, errors.ErrNoName
+		return nil, xhttp.NewError(errors.ErrNoName, http.StatusBadRequest)
+	}
+
+	start, end, err := prometheus.ParseStartAndEnd(r, h.parseOpts)
+	if err != nil {
+		return nil, err
 	}
 
 	nameBytes := []byte(name)
 	return &storage.CompleteTagsQuery{
-		// NB: necessarily spans the entire timerange for the index.
-		Start:            time.Time{},
-		End:              h.nowFn(),
+		Start:            start,
+		End:              end,
 		CompleteNameOnly: false,
 		FilterNameTags:   [][]byte{nameBytes},
 		TagMatchers: models.Matchers{
diff --git a/src/query/api/v1/handler/prometheus/remote/tag_values_test.go b/src/query/api/v1/handler/prometheus/remote/tag_values_test.go
index 120d158fdf..cf617060ae 100644
--- a/src/query/api/v1/handler/prometheus/remote/tag_values_test.go
+++ b/src/query/api/v1/handler/prometheus/remote/tag_values_test.go
@@ -44,8 +44,8 @@ import (
 )
 
 type tagValuesMatcher struct {
-	now       time.Time
-	filterTag string
+	start, end time.Time
+	filterTag  string
 }
 
 func (m *tagValuesMatcher) String() string { return "tag values query" }
@@ -55,11 +55,11 @@ func (m *tagValuesMatcher) Matches(x interface{}) bool {
 		return false
 	}
 
-	if !q.Start.Equal(time.Time{}) {
+	if !q.Start.Equal(m.start) {
 		return false
 	}
 
-	if !q.End.Equal(m.now) {
+	if !q.End.Equal(m.end) {
 		return false
 	}
 
@@ -123,7 +123,7 @@ func TestTagValues(t *testing.T) {
 	url := fmt.Sprintf("/label/{%s}/values", NameReplace)
 
 	for _, tt := range names {
-		path := fmt.Sprintf("/label/%s/values", tt.name)
+		path := fmt.Sprintf("/label/%s/values?start=100", tt.name)
 		req, err := http.NewRequest("GET", path, nil)
 		if err != nil {
 			t.Fatal(err)
@@ -132,7 +132,8 @@ func TestTagValues(t *testing.T) {
 		rr := httptest.NewRecorder()
 		router := mux.NewRouter()
 		matcher := &tagValuesMatcher{
-			now:       now,
+			start:     time.Unix(100, 0),
+			end:       now,
 			filterTag: tt.name,
 		}
 
@@ -146,7 +147,7 @@ func TestTagValues(t *testing.T) {
 			},
 			Metadata: block.ResultMetadata{
 				Exhaustive: false,
-				Warnings:   []block.Warning{block.Warning{Name: "foo", Message: "bar"}},
+				Warnings:   []block.Warning{{Name: "foo", Message: "bar"}},
 			},
 		}
 
diff --git a/src/query/parser/promql/options.go b/src/query/parser/promql/options.go
index 036da45718..1feb5105ce 100644
--- a/src/query/parser/promql/options.go
+++ b/src/query/parser/promql/options.go
@@ -21,10 +21,14 @@
 package promql
 
 import (
-	"github.com/m3db/m3/src/query/models"
-	"github.com/m3db/m3/src/query/parser"
+	"time"
+
 	"github.com/prometheus/prometheus/pkg/labels"
 	pql "github.com/prometheus/prometheus/promql/parser"
+
+	"github.com/m3db/m3/src/query/models"
+	"github.com/m3db/m3/src/query/parser"
+	xclock "github.com/m3db/m3/src/x/clock"
 )
 
 // ParseFunctionExpr parses arguments to a function expression, returning
@@ -53,28 +57,38 @@ func defaultMetricSelectorFn(query string) ([]*labels.Matcher, error) {
 	return pql.ParseMetricSelector(query)
 }
 
+func defaultNowFn() time.Time {
+	return time.Now()
+}
+
 // ParseOptions are options for the Prometheus parser.
 type ParseOptions interface {
 	// ParseFn gets the parse function.
 	ParseFn() ParseFn
 	// SetParseFn sets the parse function.
-	SetParseFn(f ParseFn) ParseOptions
+	SetParseFn(ParseFn) ParseOptions
 
 	// MetricSelectorFn gets the metric selector function.
 	MetricSelectorFn() MetricSelectorFn
 	// SetMetricSelectorFn sets the metric selector function.
-	SetMetricSelectorFn(f MetricSelectorFn) ParseOptions
+	SetMetricSelectorFn(MetricSelectorFn) ParseOptions
 
 	// FunctionParseExpr gets the parsing function.
 	FunctionParseExpr() ParseFunctionExpr
 	// SetFunctionParseExpr sets the parsing function.
-	SetFunctionParseExpr(f ParseFunctionExpr) ParseOptions
+	SetFunctionParseExpr(ParseFunctionExpr) ParseOptions
+
+	// NowFn gets the now function.
+	NowFn() xclock.NowFn
+	// SetNowFn sets the now function.
+	SetNowFn(xclock.NowFn) ParseOptions
 }
 
 type parseOptions struct {
 	parseFn     ParseFn
 	selectorFn  MetricSelectorFn
 	fnParseExpr ParseFunctionExpr
+	nowFn       xclock.NowFn
 }
 
 // NewParseOptions creates a new parse options.
@@ -83,6 +97,7 @@ func NewParseOptions() ParseOptions {
 		parseFn:     defaultParseFn,
 		selectorFn:  defaultMetricSelectorFn,
 		fnParseExpr: NewFunctionExpr,
+		nowFn:       defaultNowFn,
 	}
 }
 
@@ -115,3 +130,13 @@ func (o *parseOptions) SetFunctionParseExpr(f ParseFunctionExpr) ParseOptions {
 	opts.fnParseExpr = f
 	return &opts
 }
+
+func (o *parseOptions) NowFn() xclock.NowFn {
+	return o.nowFn
+}
+
+func (o *parseOptions) SetNowFn(f xclock.NowFn) ParseOptions {
+	opts := *o
+	opts.nowFn = f
+	return &opts
+}