diff --git a/MagickCore/string-private.h b/MagickCore/string-private.h
index 40bdb2dcc8..d44afbf736 100644
--- a/MagickCore/string-private.h
+++ b/MagickCore/string-private.h
@@ -114,6 +114,18 @@ static inline long StringToLong(const char *magick_restrict value)
   return(strtol(value,(char **) NULL,10));
 }
 
+static inline MagickOffsetType StringToMagickOffsetType(const char *string,
+  const double interval)
+{
+  double
+    value;
+
+  value=SiPrefixToDoubleInterval(string,interval);
+  if (value >= (double) MagickULLConstant(~0))
+    return((MagickOffsetType) MagickULLConstant(~0));
+  return((MagickOffsetType) value);
+}
+
 static inline MagickSizeType StringToMagickSizeType(const char *string,
   const double interval)
 {
diff --git a/MagickCore/timer.c b/MagickCore/timer.c
index 7ed577a6aa..59aad7d643 100644
--- a/MagickCore/timer.c
+++ b/MagickCore/timer.c
@@ -360,17 +360,17 @@ MagickExport time_t GetMagickTime(void)
       const char
         *source_date_epoch;
 
-      epoch_initialized=MagickTrue;
       source_date_epoch=getenv("SOURCE_DATE_EPOCH");
       if (source_date_epoch != (const char *) NULL)
         {
           time_t
             epoch;
 
-          epoch=(time_t) StringToUnsignedLong(source_date_epoch);
+          epoch=(time_t) StringToMagickOffsetType(source_date_epoch,100.0);
           if ((epoch > 0) && (epoch <= time((time_t *) NULL)))
             magick_epoch=epoch;
         }
+      epoch_initialized=MagickTrue;
     }
   if (magick_epoch != 0)
     return(magick_epoch);