--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/backend/src/main/java/org/dive4elements/river/backend/utils/DateGuesser.java	Thu Sep 04 15:03:25 2014 +0200
@@ -0,0 +1,266 @@
+/* Copyright (C) 2011, 2012, 2013 by Bundesanstalt für Gewässerkunde
+ * Software engineering by Intevation GmbH
+ *
+ * This file is Free Software under the GNU AGPL (>=v3)
+ * and comes with ABSOLUTELY NO WARRANTY! Check out the
+ * documentation coming with Dive4Elements River for details.
+ */
+
+package org.dive4elements.river.backend.utils;
+
+import java.util.Date;
+import java.util.Calendar;
+
+import java.util.regex.Pattern;
+import java.util.regex.Matcher;
+
+public final class DateGuesser {
+    public static final String [] MONTH = {
+        "jan", "feb", "mrz", "apr", "mai", "jun",
+        "jul", "aug", "sep", "okt", "nov", "dez"
+    };
+
+    public static final int guessMonth(String s) {
+        s = s.toLowerCase();
+        for (int i = 0; i < MONTH.length; ++i)
+            if (MONTH[i].equals(s)) {
+                return i;
+            }
+        return -1;
+    }
+
+    public static final Pattern YYYY_MM_DD =
+        Pattern.compile("^(\\d{4})-(\\d{2})-(\\d{2})$");
+
+    public static final Pattern DD_MM_YYYY =
+        Pattern.compile("^(\\d{1,2})\\.(\\d{1,2})\\.(\\d{2,4})$");
+
+    public static final Pattern MMM_YYYY =
+        Pattern.compile("^(\\d{0,2})\\.?(\\w{3})\\.?(\\d{2,4})$");
+
+    public static final Pattern GARBAGE_YYYY =
+        Pattern.compile("^\\D*(\\d{2,4})$");
+
+    public static final Pattern YYYY_MM_DDThh_mm =
+        Pattern.compile("^(\\d{4})-(\\d{2})-(\\d{2})T(\\d{2}):(\\d{2})$");
+
+    public static final Pattern YYYY_MM_DDThh_mm_ss =
+        Pattern.compile("^(\\d{4})-(\\d{2})-(\\d{2})T(\\d{2}):(\\d{2}):(\\d{2})$");
+
+    public static final Pattern DD_MM_YYYYThh_mm =
+        Pattern.compile("^(\\d{1,2})\\.(\\d{1,2})\\.(\\d{2,4})T(\\d{1,2}):(\\d{2})$");
+
+    public static final Pattern DD_MM_YYYYThh_mm_ss =
+        Pattern.compile("^(\\d{1,2})\\.(\\d{1,2})\\.(\\d{2,4})T(\\d{1,2}):(\\d{2}):(\\d{2})$");
+
+    public static final Pattern DDMMYY =
+        Pattern.compile("^(\\d{2})(\\d{2})(\\d{2})$");
+
+    private DateGuesser() {
+    }
+
+    public static final int calendarMonth(String month) {
+        return calendarMonth(Integer.parseInt(month));
+    }
+
+    public static final int calendarMonth(int month) {
+        return Math.max(Math.min(month-1, 11), 0);
+    }
+
+    /**
+     * Guess date by trying all different patterns.
+     * Throws IllegalArgumentException if not able to guess.
+     * @param s The date to be guessed (e.g. 11.02.2001).
+     * @return the parsed Date.
+     */
+    public static Date guessDate(String s) {
+        if (s == null || (s = s.trim()).length() == 0) {
+            throw new IllegalArgumentException();
+        }
+
+        Matcher m;
+
+        m = YYYY_MM_DD.matcher(s);
+
+        if (m.matches()) {
+            Calendar cal = Calendar.getInstance();
+            String year  = m.group(1);
+            String month = m.group(2);
+            String day   = m.group(3);
+            cal.clear();
+            cal.set(
+                Integer.parseInt(year),
+                calendarMonth(month),
+                Integer.parseInt(day),
+                12, 0, 0);
+            return cal.getTime();
+        }
+
+        m = DD_MM_YYYY.matcher(s);
+
+        if (m.matches()) {
+            Calendar cal = Calendar.getInstance();
+            String year  = m.group(3);
+            String month = m.group(2);
+            String day   = m.group(1);
+            cal.clear();
+            cal.set(
+                Integer.parseInt(year) + (year.length() == 2 ? 1900 : 0),
+                calendarMonth(month),
+                Integer.parseInt(day),
+                12, 0, 0);
+            return cal.getTime();
+        }
+
+        m = MMM_YYYY.matcher(s);
+
+        if (m.matches()) {
+            int month = guessMonth(m.group(2));
+            if (month >= 0) {
+                Calendar cal = Calendar.getInstance();
+                String year = m.group(3);
+                String day  = m.group(1);
+                cal.clear();
+                cal.set(
+                    Integer.parseInt(year) + (year.length() == 2 ? 1900 : 0),
+                    month,
+                    day.length() == 0 ? 15 : Integer.parseInt(day),
+                    12, 0, 0);
+                return cal.getTime();
+            }
+        }
+
+        m = YYYY_MM_DDThh_mm.matcher(s);
+
+        if (m.matches()) {
+            Calendar cal = Calendar.getInstance();
+            String year = m.group(1);
+            String month = m.group(2);
+            String day = m.group(3);
+            String hour = m.group(4);
+            String minute = m.group(5);
+            cal.clear();
+            cal.set(
+                Integer.parseInt(year),
+                calendarMonth(month),
+                Integer.parseInt(day),
+                Integer.parseInt(hour),
+                Integer.parseInt(minute),
+                0
+            );
+            return cal.getTime();
+        }
+
+        m = YYYY_MM_DDThh_mm_ss.matcher(s);
+
+        if (m.matches()) {
+            Calendar cal = Calendar.getInstance();
+            String year = m.group(1);
+            String month = m.group(2);
+            String day = m.group(3);
+            String hour = m.group(4);
+            String minute = m.group(5);
+            String second = m.group(6);
+            cal.clear();
+            cal.set(
+                Integer.parseInt(year),
+                calendarMonth(month),
+                Integer.parseInt(day),
+                Integer.parseInt(hour),
+                Integer.parseInt(minute),
+                Integer.parseInt(second)
+            );
+            return cal.getTime();
+        }
+
+        m = DD_MM_YYYYThh_mm.matcher(s);
+
+        if (m.matches()) {
+            Calendar cal = Calendar.getInstance();
+            String year = m.group(3);
+            String month = m.group(2);
+            String day = m.group(1);
+            String hour = m.group(4);
+            String minute = m.group(5);
+            cal.clear();
+            cal.set(
+                Integer.parseInt(year) + (year.length() == 2 ? 1900 : 0),
+                calendarMonth(month),
+                Integer.parseInt(day),
+                Integer.parseInt(hour),
+                Integer.parseInt(minute),
+                0
+            );
+            return cal.getTime();
+        }
+
+        m = DD_MM_YYYYThh_mm_ss.matcher(s);
+
+        if (m.matches()) {
+            Calendar cal = Calendar.getInstance();
+            String year = m.group(3);
+            String month = m.group(2);
+            String day = m.group(1);
+            String hour = m.group(4);
+            String minute = m.group(5);
+            String second = m.group(6);
+            cal.clear();
+            cal.set(
+                Integer.parseInt(year) + (year.length() == 2 ? 1900 : 0),
+                calendarMonth(month),
+                Integer.parseInt(day),
+                Integer.parseInt(hour),
+                Integer.parseInt(minute),
+                Integer.parseInt(second)
+            );
+            return cal.getTime();
+        }
+
+        m = DDMMYY.matcher(s);
+
+        if (m.matches()) {
+            Calendar cal = Calendar.getInstance();
+            String day   = m.group(1);
+            String month = m.group(2);
+            String yearS = m.group(3);
+            int year = Integer.parseInt(yearS);
+
+            if (year <= cal.get(Calendar.YEAR) % 100) {
+                year += 2000;
+            }
+            else {
+                year += 1900;
+            }
+            cal.clear();
+            cal.set(
+                year,
+                Integer.parseInt(month),  // month
+                Integer.parseInt(day), // day
+                12, 0, 0);
+            return cal.getTime();
+        }
+
+        m = GARBAGE_YYYY.matcher(s);
+
+        if (m.matches()) {
+            Calendar cal = Calendar.getInstance();
+            String year = m.group(1);
+            cal.clear();
+            cal.set(
+                Integer.parseInt(year) + (year.length() == 2 ? 1900 : 0),
+                5,  // month
+                15, // day
+                12, 0, 0);
+            return cal.getTime();
+        }
+
+        throw new IllegalArgumentException();
+    }
+
+    public static void main(String [] args) {
+        for (int i = 0; i < args.length; ++i) {
+            System.out.println(args[i] + ": " + guessDate(args[i]));
+        }
+    }
+}
+// end of file