diff --git a/pylot/core/analysis/magnitude.py b/pylot/core/analysis/magnitude.py
index a22dbeba..8635fbc9 100644
--- a/pylot/core/analysis/magnitude.py
+++ b/pylot/core/analysis/magnitude.py
@@ -15,6 +15,7 @@ from scipy.optimize import curve_fit
 from scipy import integrate, signal
 from pylot.core.io.data import Data
 from pylot.core.util.dataprocessing import restitute_data
+from pylot.core.util.utils import common_range
 
 
 class Magnitude(object):
@@ -360,25 +361,8 @@ def calcsourcespec(wfstream, onset, inventory, vp, delta, azimuth, incidence, qp
         cordat_copy = cordat.copy()
         # get equal time stamps and lengths of traces
         # necessary for rotation of traces
-        tr0start = cordat_copy[0].stats.starttime
-        tr0start = tr0start.timestamp
-        tr0end = cordat_copy[0].stats.endtime
-        tr0end = tr0end.timestamp
-        tr1start = cordat_copy[1].stats.starttime
-        tr1start = tr1start.timestamp
-        tr1end = cordat_copy[1].stats.endtime
-        tr1end = tr1end.timestamp
-        tr2start = cordat_copy[2].stats.starttime
-        tr2start = tr2start.timestamp
-        tr2end = cordat_copy[0].stats.endtime
-        tr2end = tr2end.timestamp
-        trstart = UTCDateTime(max([tr0start, tr1start, tr2start]))
-        trend = UTCDateTime(min([tr0end, tr1end, tr2end]))
+        trstart, trend = common_range(cordat_copy)
         cordat_copy.trim(trstart, trend)
-        minlen = min([len(cordat_copy[0]), len(cordat_copy[1]), len(cordat_copy[2])])
-        cordat_copy[0].data = cordat_copy[0].data[0:minlen]
-        cordat_copy[1].data = cordat_copy[1].data[0:minlen]
-        cordat_copy[2].data = cordat_copy[2].data[0:minlen]
         try:
             # rotate into LQT (ray-coordindate-) system using Obspy's rotate
             # L: P-wave direction
diff --git a/pylot/core/util/utils.py b/pylot/core/util/utils.py
index 3c210da9..5045d4b1 100644
--- a/pylot/core/util/utils.py
+++ b/pylot/core/util/utils.py
@@ -206,6 +206,24 @@ def four_digits(year):
     return year
 
 
+def common_range(stream):
+    '''
+    takes a stream object and returns the earliest end and the latest start
+    time of all contained trace objects
+    :param stream: seismological data stream
+    :type stream: `~obspy.core.stream.Stream`
+    :return: maximum start time and minimum end time
+    '''
+    max_start = None
+    min_end = None
+    for trace in stream:
+        if max_start is None or trace.stats.starttime > max_start:
+            max_start = trace.stats.starttime
+        if min_end is None or trace.stats.endtime < min_end:
+            min_end = trace.stats.endtime
+    return max_start, min_end
+
+
 def full_range(stream):
     '''
     takes a stream object and returns the latest end and the earliest start