diff --git a/lmwsip.py b/lmwsip.py
index 73c8262..9fc7bfc 100644
--- a/lmwsip.py
+++ b/lmwsip.py
@@ -8,6 +8,8 @@ import select
 import time
 import re
 import logging
+from datetime import datetime, timedelta
+from dateutil import tz
 
 class LmwSip:
     """Class to connect to the LMW Standard Interface prototcol (sip)
@@ -272,6 +274,71 @@ Returns a single string value or None
         #
         return(value)
 
+    def _lmwdelta_(self, startTime, endTime):
+        d = endTime - startTime
+        h = 24*d.days + d.seconds // 3600
+        m = (d.seconds % 3600)//60
+        return("+%02i:%02i" % (h, m))
+
+    def timeSerie(self, process, location, parameter,
+                        startTime, endTime, cmd_type="DATB"):
+        """timeSerie(process, location, parameter, startTime, endTime, cmd_type="DATA")
+
+Parameters:
+    process:      <WN|VW|AS>
+    location:     <lmw location (e.g. HOEK)>
+    parameter:    <lmw parameter (e.g. H10)>
+    startTime:    Start time (datetime)
+    endTime:      End time (datetime)
+    cmd_type:     [DATA|DATB]
+
+startTime is rounded up to the next measurement time.
+So 12:00:00.000001 --> 12:00:10.00.0
+
+The times should have correct timezone information. Otherwise local timezone
+is assumed. Timezones are converted to 'GMT+1' for the sip commands.
+
+Example:
+    lmw.data_string("WN", "HOEK", "H10", ...)
+ 
+Returns a LmwtimeSerie object
+
+Errors:
+    startTime > endTime
+    endTime - startTime > 24 hour
+    now - startTime < 30 days
+"""
+        startTime = startTime.astimezone(tz.gettz('GMT+1'))
+        endTime   = endTime.astimezone(tz.gettz('GMT+1'))
+
+        startTime += timedelta(microseconds=1000000-startTime.microsecond)
+        startTime += timedelta(seconds=60-startTime.second)
+        if (parameter.find("10") != -1):
+            if startTime.minute % 10 != 0:
+                delta = timedelta(minutes=10)
+                startTime += timedelta(minutes=(10-startTime.minute%10))
+        else:
+            delta = timedelta(minutes=1)
+
+        if startTime > endTime:
+            raise sipTimeSeriesError(startTime, endTime,
+                                     "starttime > endtime")
+        if endTime - startTime > timedelta(days=1): 
+            raise sipTimeSeriesError(startTime, endTime,
+                                     "endtime - starttime > 24 hour")
+        if datetime.now(tz=tz.gettz('GMT+1')) - startTime > timedelta(days=30): 
+            raise sipTimeSeriesError(startTime, endTime,
+                                     "now - starttime > 30 days")
+        if process == "VW":
+            cmd_type="DATA"
+
+        values = self.cmd(process, location, parameter,
+                          self._lmwdelta_(startTime, endTime),
+                          startTime.strftime("%d-%m-%Y"),
+                          startTime.strftime("%H:%M"),
+                          cmd_type)
+        return(lmwTimeSerie(startTime, delta, values))
+
     def logout(self):
         """logout()
 
@@ -280,6 +347,28 @@ Logs of
         self.send("LO\r")
         self.closesocket()
 
+class lmwTimeSerie:
+    def __init__(self, start, delta, values):
+        self.ts = []
+        self.addvalues(start, delta, values)
+
+    def addvalues(self, start, delta, values):
+        for e in values.split(";"):
+            a = [ start ]
+            a.append(e.split("/"))
+            self.ts.append(a)
+            start += delta
+
+class sipTimeSeriesError(Exception):
+    """Parameter errors for timeSeries"""
+    def __init__(self, startTime, endTime, message):
+        self.startTime = startTime
+        self.endTime   = endTime
+        self.message   = message
+
+    def __str__(self):
+        return("%s\n  starttime: %s\n  end time:  %s" %
+                              (self.message, self.startTime, self.endTime))
 
 class LmwSipConnectError(Exception):
     """Connection exceptions for LmwSip"""