diff --git a/gateway/airkaz/airkaz.go b/gateway/airkaz/airkaz.go
index 484718f..4ee4bb2 100644
--- a/gateway/airkaz/airkaz.go
+++ b/gateway/airkaz/airkaz.go
@@ -4,6 +4,7 @@ import (
 	"encoding/json"
 	"github.com/hg/airmon/influx"
 	"github.com/hg/airmon/net"
+	"github.com/hg/airmon/storage"
 	"github.com/hg/airmon/tm"
 	influxdb2 "github.com/influxdata/influxdb-client-go/v2"
 	"github.com/pkg/errors"
@@ -34,42 +35,87 @@ type measurement struct {
 	Hour     string   `json:"hour"`
 }
 
+type lastUpdates map[int64]tm.Time
+
+type collector struct {
+	sender      *influx.MeasurementSender
+	client      *net.Client
+	lastUpdates lastUpdates
+}
+
+const lastUpdatesFilename = "airkaz-times.json"
+
 func Collect(sender *influx.MeasurementSender) {
-	client := net.NewProxiedClient()
-	lastUpdates := map[int64]tm.Time{}
+	col := collector{
+		sender:      sender,
+		client:      net.NewProxiedClient(),
+		lastUpdates: lastUpdates{},
+	}
+
+	if last := loadLastUpdates(); last != nil {
+		col.lastUpdates = *last
+	}
 
 	for {
-		if measurements, err := getResponse(client); err == nil {
-			log.Print("found ", len(measurements), " airkaz measurements")
-
-			toSave := make([]*measurement, len(measurements))
-
-			for _, meas := range measurements {
-				if meas.Error != 0 || meas.Status != "active" || meas.Hour != "now" {
-					continue
-				}
-				if last, ok := lastUpdates[meas.Id]; ok && last == meas.Date {
-					continue
-				}
-				lastUpdates[meas.Id] = meas.Date
-				toSave = append(toSave, meas)
-			}
-
-			go func() {
-				for _, ms := range toSave {
-					saveMeasurement(ms, sender)
-				}
-			}()
-		} else {
-			log.Print("could not get response from airkaz: ", err)
+		if err := col.run(); err != nil {
+			log.Print("could not save airkaz data: ", err)
 		}
-
 		time.Sleep(5 * time.Minute)
 	}
 }
 
-func getResponse(client *net.Client) ([]*measurement, error) {
-	body, err := client.Get("https://airkaz.org/")
+func loadLastUpdates() *lastUpdates {
+	var lu *lastUpdates
+
+	err := storage.Load(lastUpdatesFilename, &lu)
+	if err != nil {
+		lu = nil
+		log.Print("could not load airkaz update times: ", err)
+	}
+
+	return lu
+}
+
+func (c *collector) saveLastUpdates() {
+	if err := storage.Save(lastUpdatesFilename, c.lastUpdates); err != nil {
+		log.Print("could not save airkaz update times: ", err)
+	}
+}
+
+func (c *collector) run() error {
+	measurements, err := c.getResponse()
+	if err != nil {
+		return err
+	}
+
+	log.Print("found ", len(measurements), " airkaz measurements")
+
+	toSave := make([]measurement, len(measurements))
+
+	for _, meas := range measurements {
+		if meas.Error != 0 || meas.Status != "active" || meas.Hour != "now" {
+			continue
+		}
+		if last, ok := c.lastUpdates[meas.Id]; ok && !meas.Date.After(last.Time) {
+			continue
+		}
+		c.lastUpdates[meas.Id] = meas.Date
+		toSave = append(toSave, meas)
+	}
+
+	go c.saveLastUpdates()
+
+	go func() {
+		for _, ms := range toSave {
+			c.saveMeasurement(&ms)
+		}
+	}()
+
+	return nil
+}
+
+func (c *collector) getResponse() ([]measurement, error) {
+	body, err := c.client.Get("https://airkaz.org/")
 	if err != nil {
 		return nil, err
 	}
@@ -79,7 +125,7 @@ func getResponse(client *net.Client) ([]*measurement, error) {
 		return nil, errors.Wrap(err, "measurement json not found in response")
 	}
 
-	var measurements []*measurement
+	var measurements []measurement
 	if err = json.Unmarshal(matches[1], &measurements); err != nil {
 		return nil, errors.Wrap(err, "could not parse response: ")
 	}
@@ -87,25 +133,28 @@ func getResponse(client *net.Client) ([]*measurement, error) {
 	return measurements, nil
 }
 
-func saveMeasurement(meas *measurement, sender *influx.MeasurementSender) {
+func (c *collector) saveMeasurement(meas *measurement) {
 	tags := map[string]string{
 		"city":    meas.City,
 		"station": meas.Name,
 	}
 
 	save := func(kind string, fields map[string]interface{}) {
-		sender.Send(influxdb2.NewPoint(kind, tags, fields, meas.Date.Time))
+		c.sender.Send(influxdb2.NewPoint(kind, tags, fields, meas.Date.Time))
 	}
 
-	if meas.Pm25Curr != nil && meas.Pm10Curr != nil {
-		save("airkaz:particulates", map[string]interface{}{
-			"pm25": uint16(*meas.Pm25Curr),
-			"pm10": uint16(*meas.Pm10Curr),
-		})
+	pmData := make(map[string]interface{})
+	if meas.Pm25Curr != nil {
+		pmData["pm25"] = uint16(*meas.Pm25Curr)
+	}
+	if meas.Pm10Curr != nil {
+		pmData["pm10"] = uint16(*meas.Pm10Curr)
+	}
+	if len(pmData) > 0 {
+		save("airkaz:particulates", pmData)
 	}
 
-	tempData := map[string]interface{}{}
-
+	tempData := make(map[string]interface{})
 	if meas.TempCurr != nil {
 		tempData["temperature"] = *meas.TempCurr
 	}
@@ -115,7 +164,6 @@ func saveMeasurement(meas *measurement, sender *influx.MeasurementSender) {
 	if meas.Press != nil {
 		tempData["pressure"] = *meas.Press
 	}
-
 	if len(tempData) > 0 {
 		save("airkaz:temperature", tempData)
 	}
diff --git a/gateway/settings/settings.go b/gateway/settings/settings.go
index 17843cf..0e66fdf 100644
--- a/gateway/settings/settings.go
+++ b/gateway/settings/settings.go
@@ -1,3 +1 @@
 package settings
-
-
diff --git a/gateway/tm/tm.go b/gateway/tm/tm.go
index 34c511a..33d01f5 100644
--- a/gateway/tm/tm.go
+++ b/gateway/tm/tm.go
@@ -21,6 +21,14 @@ func init() {
 	}
 }
 
+func (t *Time) MarshalJSON() ([]byte, error) {
+	if t == nil {
+		return []byte("null"), nil
+	}
+	formatted := t.Time.Format(timeFormat)
+	return []byte(formatted), nil
+}
+
 func (t *Time) UnmarshalJSON(b []byte) (err error) {
 	s := strings.Trim(string(b), `"`)
 	if s == "null" {