From c8c60e02eaf5febc25d4fb86635d2f48c8776c63 Mon Sep 17 00:00:00 2001
From: Peter Killick <peter.killick@metoffice.gov.uk>
Date: Fri, 10 Feb 2017 10:27:15 +0000
Subject: [PATCH] Gracefully handle long time intervals

---
 lib/iris/coords.py                       |  8 +++++++-
 lib/iris/tests/unit/coords/test_Coord.py | 24 ++++++++++++++++++++++++
 2 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/lib/iris/coords.py b/lib/iris/coords.py
index c1686f90219..c4dab0fabe8 100644
--- a/lib/iris/coords.py
+++ b/lib/iris/coords.py
@@ -732,7 +732,13 @@ def __str__(self):
             fmt = '{cls}({points}{bounds}' \
                   ', standard_name={self.standard_name!r}' \
                   ', calendar={self.units.calendar!r}{other_metadata})'
-            points = self._str_dates(self.points)
+            if self.units.is_long_time_interval():
+                # A time unit with a long time interval ("months" or "years")
+                # cannot be converted to a date using `num2date` so gracefully
+                # fall back to printing points as numbers, not datetimes.
+                points = self.points
+            else:
+                points = self._str_dates(self.points)
             bounds = ''
             if self.has_bounds():
                 bounds = ', bounds=' + self._str_dates(self.bounds)
diff --git a/lib/iris/tests/unit/coords/test_Coord.py b/lib/iris/tests/unit/coords/test_Coord.py
index bc3c4e3a656..779438170e2 100644
--- a/lib/iris/tests/unit/coords/test_Coord.py
+++ b/lib/iris/tests/unit/coords/test_Coord.py
@@ -323,5 +323,29 @@ def test_convert_unknown_units(self):
         with self.assertRaisesRegexp(UnitConversionError, emsg):
             coord.convert_units('degrees')
 
+class Test___str__(tests.IrisTest):
+
+    def test_short_time_interval(self):
+        coord = DimCoord([5], standard_name='time',
+                         units='days since 1970-01-01')
+        expected = ("DimCoord([1970-01-06 00:00:00], standard_name='time', "
+                    "calendar='gregorian')")
+        result = coord.__str__()
+        self.assertEqual(expected, result)
+
+    def test_long_time_interval(self):
+        coord = DimCoord([5], standard_name='time',
+                         units='years since 1970-01-01')
+        expected = "DimCoord([5], standard_name='time', calendar='gregorian')"
+        result = coord.__str__()
+        self.assertEqual(expected, result)
+
+    def test_non_time_unit(self):
+        coord = DimCoord([1.])
+        expected = repr(coord)
+        result = coord.__str__()
+        self.assertEqual(expected, result)
+
+
 if __name__ == '__main__':
     tests.main()