PP Proleptic Gregorian

lib/iris/fileformats/pp.py

@@ -1078,7 +1078,7 @@ def core_data(self):
     def calendar(self):
         """Return the calendar of the field."""
         # TODO #577 What calendar to return when ibtim.ic in [0, 3]
-        calendar = cf_units.CALENDAR_STANDARD
+        calendar = cf_units.CALENDAR_PROLEPTIC_GREGORIAN
         if self.lbtim.ic == 2:
             calendar = cf_units.CALENDAR_360_DAY
         elif self.lbtim.ic == 4:

lib/iris/fileformats/pp_load_rules.py

@@ -503,6 +503,13 @@ def _new_coord_and_dims(
         a new (coordinate, dims) pair.
 
     """
+    if (
+        units.is_time_reference()
+        and units.calendar == cf_units.CALENDAR_PROLEPTIC_GREGORIAN
+    ):
+        units = cf_units.Unit(
+            "hours since epoch", calendar=cf_units.CALENDAR_STANDARD
+        )
     bounds = lower_and_upper_bounds
     if is_vector_operation:
         dims, points, bounds = _reduce_points_and_bounds(points, bounds)
@@ -548,7 +555,7 @@ def _epoch_date_hours_internals(epoch_hours_unit, datetime):
         if m == 0:
             # Add a 'January', by changing month=0 to 1.
             m = 1
-            if calendar == cf_units.CALENDAR_STANDARD:
+            if calendar == cf_units.CALENDAR_PROLEPTIC_GREGORIAN:
                 days_offset += 31
             elif calendar == cf_units.CALENDAR_360_DAY:
                 days_offset += 30
@@ -561,7 +568,7 @@ def _epoch_date_hours_internals(epoch_hours_unit, datetime):
         if y == 0:
             # Add a 'Year 0', by changing year=0 to 1.
             y = 1
-            if calendar == cf_units.CALENDAR_STANDARD:
+            if calendar == cf_units.CALENDAR_PROLEPTIC_GREGORIAN:
                 days_in_year_0 = 366
             elif calendar == cf_units.CALENDAR_360_DAY:
                 days_in_year_0 = 360

lib/iris/fileformats/pp_save_rules.py

@@ -114,6 +114,11 @@ def _general_time_rules(cube, pp):
     frt_coord = scalar_coord(cube, "forecast_reference_time")
     clim_season_coord = scalar_coord(cube, "clim_season")
 
+    if time_coord is not None:
+        time_unit = time_coord.units
+        if time_unit.calendar == "standard":
+            time_unit = time_unit.change_calendar("proleptic_gregorian")
+
     cm_time_mean = scalar_cell_method(cube, "mean", "time")
     cm_time_min = scalar_cell_method(cube, "minimum", "time")
     cm_time_max = scalar_cell_method(cube, "maximum", "time")
@@ -122,7 +127,7 @@ def _general_time_rules(cube, pp):
     if time_coord is not None and fp_coord is None and frt_coord is None:
         pp.lbtim.ia = 0
         pp.lbtim.ib = 0
-        pp.t1 = time_coord.units.num2date(time_coord.points[0])
+        pp.t1 = time_unit.num2date(time_coord.points[0])
         pp.t2 = cftime.datetime(0, 0, 0, calendar=None, has_year_zero=True)
 
     # Forecast.
@@ -133,10 +138,8 @@ def _general_time_rules(cube, pp):
     ):
         pp.lbtim.ia = 0
         pp.lbtim.ib = 1
-        pp.t1 = time_coord.units.num2date(time_coord.points[0])
-        pp.t2 = time_coord.units.num2date(
-            time_coord.points[0] - fp_coord.points[0]
-        )
+        pp.t1 = time_unit.num2date(time_coord.points[0])
+        pp.t2 = time_unit.num2date(time_coord.points[0] - fp_coord.points[0])
         pp.lbft = fp_coord.points[0]
 
     # Time mean (non-climatological).
@@ -151,8 +154,8 @@ def _general_time_rules(cube, pp):
         # XXX How do we know *which* time to use if there are more than
         # one? *Can* there be more than one?
         pp.lbtim.ib = 2
-        pp.t1 = time_coord.units.num2date(time_coord.bounds[0, 0])
-        pp.t2 = time_coord.units.num2date(time_coord.bounds[0, 1])
+        pp.t1 = time_unit.num2date(time_coord.bounds[0, 0])
+        pp.t2 = time_unit.num2date(time_coord.bounds[0, 1])
         pp.lbft = fp_coord.units.convert(fp_coord.bounds[0, 1], "hours")
 
     if (
@@ -164,8 +167,8 @@ def _general_time_rules(cube, pp):
     ):
         # Handle missing forecast period using time and forecast ref time.
         pp.lbtim.ib = 2
-        pp.t1 = time_coord.units.num2date(time_coord.bounds[0, 0])
-        pp.t2 = time_coord.units.num2date(time_coord.bounds[0, 1])
+        pp.t1 = time_unit.num2date(time_coord.bounds[0, 0])
+        pp.t2 = time_unit.num2date(time_coord.bounds[0, 1])
         stop = time_coord.units.convert(
             time_coord.bounds[0, 1], "hours since epoch"
         )
@@ -181,8 +184,8 @@ def _general_time_rules(cube, pp):
         and cm_time_mean is not None
     ):
         pp.lbtim.ib = 2
-        pp.t1 = time_coord.units.num2date(time_coord.bounds[0, 0])
-        pp.t2 = time_coord.units.num2date(time_coord.bounds[0, 1])
+        pp.t1 = time_unit.num2date(time_coord.bounds[0, 0])
+        pp.t2 = time_unit.num2date(time_coord.bounds[0, 1])
 
     if (
         time_coord is not None
@@ -238,12 +241,8 @@ def _general_time_rules(cube, pp):
         pp.lbtim.ia = int(cm_time_max.intervals[0][:-5])
 
     if time_coord is not None and time_coord.has_bounds():
-        lower_bound_yr = time_coord.units.num2date(
-            time_coord.bounds[0, 0]
-        ).year
-        upper_bound_yr = time_coord.units.num2date(
-            time_coord.bounds[0, 1]
-        ).year
+        lower_bound_yr = time_unit.num2date(time_coord.bounds[0, 0]).year
+        upper_bound_yr = time_unit.num2date(time_coord.bounds[0, 1]).year
     else:
         lower_bound_yr = None
         upper_bound_yr = None
@@ -261,8 +260,8 @@ def _general_time_rules(cube, pp):
         # Climatological time mean - single year.
         pp.lbtim.ia = 0
         pp.lbtim.ib = 2
-        pp.t1 = time_coord.units.num2date(time_coord.bounds[0, 0])
-        pp.t2 = time_coord.units.num2date(time_coord.bounds[0, 1])
+        pp.t1 = time_unit.num2date(time_coord.bounds[0, 0])
+        pp.t2 = time_unit.num2date(time_coord.bounds[0, 1])
         pp.lbft = fp_coord.units.convert(fp_coord.bounds[0, 1], "hours")
 
     elif (
@@ -278,19 +277,19 @@ def _general_time_rules(cube, pp):
         # Climatological time mean - spanning years - djf.
         pp.lbtim.ia = 0
         pp.lbtim.ib = 3
-        pp.t1 = time_coord.units.num2date(time_coord.bounds[0, 0])
-        pp.t2 = time_coord.units.num2date(time_coord.bounds[0, 1])
+        pp.t1 = time_unit.num2date(time_coord.bounds[0, 0])
+        pp.t2 = time_unit.num2date(time_coord.bounds[0, 1])
         if pp.t1.month == 12:
             pp.t1 = cftime.datetime(pp.t1.year, 12, 1, 0, 0, 0)
         else:
             pp.t1 = cftime.datetime(pp.t1.year - 1, 12, 1, 0, 0, 0)
         pp.t2 = cftime.datetime(pp.t2.year, 3, 1, 0, 0, 0)
         _conditional_warning(
-            time_coord.bounds[0, 0] != time_coord.units.date2num(pp.t1),
+            time_coord.bounds[0, 0] != time_unit.date2num(pp.t1),
             "modified t1 for climatological seasonal mean",
         )
         _conditional_warning(
-            time_coord.bounds[0, 1] != time_coord.units.date2num(pp.t2),
+            time_coord.bounds[0, 1] != time_unit.date2num(pp.t2),
             "modified t2 for climatological seasonal mean",
         )
         pp.lbft = fp_coord.units.convert(fp_coord.bounds[0, 1], "hours")
@@ -309,16 +308,16 @@ def _general_time_rules(cube, pp):
         pp.lbtim.ia = 0
         pp.lbtim.ib = 3
         # TODO: wut?
-        pp.t1 = time_coord.units.num2date(time_coord.bounds[0, 0])
-        pp.t2 = time_coord.units.num2date(time_coord.bounds[0, 1])
+        pp.t1 = time_unit.num2date(time_coord.bounds[0, 0])
+        pp.t2 = time_unit.num2date(time_coord.bounds[0, 1])
         pp.t1 = cftime.datetime(pp.t1.year, 3, 1, 0, 0, 0)
         pp.t2 = cftime.datetime(pp.t2.year, 6, 1, 0, 0, 0)
         _conditional_warning(
-            time_coord.bounds[0, 0] != time_coord.units.date2num(pp.t1),
+            time_coord.bounds[0, 0] != time_unit.date2num(pp.t1),
             "modified t1 for climatological seasonal mean",
         )
         _conditional_warning(
-            time_coord.bounds[0, 1] != time_coord.units.date2num(pp.t2),
+            time_coord.bounds[0, 1] != time_unit.date2num(pp.t2),
             "modified t2 for climatological seasonal mean",
         )
         pp.lbft = fp_coord.units.convert(fp_coord.bounds[0, 1], "hours")
@@ -337,16 +336,16 @@ def _general_time_rules(cube, pp):
         pp.lbtim.ia = 0
         pp.lbtim.ib = 3
         # TODO: wut?
-        pp.t1 = time_coord.units.num2date(time_coord.bounds[0, 0])
-        pp.t2 = time_coord.units.num2date(time_coord.bounds[0, 1])
+        pp.t1 = time_unit.num2date(time_coord.bounds[0, 0])
+        pp.t2 = time_unit.num2date(time_coord.bounds[0, 1])
         pp.t1 = cftime.datetime(pp.t1.year, 6, 1, 0, 0, 0)
         pp.t2 = cftime.datetime(pp.t2.year, 9, 1, 0, 0, 0)
         _conditional_warning(
-            time_coord.bounds[0, 0] != time_coord.units.date2num(pp.t1),
+            time_coord.bounds[0, 0] != time_unit.date2num(pp.t1),
             "modified t1 for climatological seasonal mean",
         )
         _conditional_warning(
-            time_coord.bounds[0, 1] != time_coord.units.date2num(pp.t2),
+            time_coord.bounds[0, 1] != time_unit.date2num(pp.t2),
             "modified t2 for climatological seasonal mean",
         )
         pp.lbft = fp_coord.units.convert(fp_coord.bounds[0, 1], "hours")
@@ -365,16 +364,16 @@ def _general_time_rules(cube, pp):
         pp.lbtim.ia = 0
         pp.lbtim.ib = 3
         # TODO: wut?
-        pp.t1 = time_coord.units.num2date(time_coord.bounds[0, 0])
-        pp.t2 = time_coord.units.num2date(time_coord.bounds[0, 1])
+        pp.t1 = time_unit.num2date(time_coord.bounds[0, 0])
+        pp.t2 = time_unit.num2date(time_coord.bounds[0, 1])
         pp.t1 = cftime.datetime(pp.t1.year, 9, 1, 0, 0, 0)
         pp.t2 = cftime.datetime(pp.t2.year, 12, 1, 0, 0, 0)
         _conditional_warning(
-            time_coord.bounds[0, 0] != time_coord.units.date2num(pp.t1),
+            time_coord.bounds[0, 0] != time_unit.date2num(pp.t1),
             "modified t1 for climatological seasonal mean",
         )
         _conditional_warning(
-            time_coord.bounds[0, 1] != time_coord.units.date2num(pp.t2),
+            time_coord.bounds[0, 1] != time_unit.date2num(pp.t2),
             "modified t2 for climatological seasonal mean",
         )
         pp.lbft = fp_coord.units.convert(fp_coord.bounds[0, 1], "hours")
@@ -398,7 +397,7 @@ def _calendar_rules(cube, pp):
     if time_coord is not None:
         if time_coord.units.calendar == "360_day":
             pp.lbtim.ic = 2
-        elif time_coord.units.calendar == "standard":
+        elif time_coord.units.calendar in ["standard", "proleptic_gregorian"]:
             pp.lbtim.ic = 1
         elif time_coord.units.calendar == "365_day":
             pp.lbtim.ic = 4

lib/iris/tests/unit/fileformats/pp/test_PPField.py

@@ -143,7 +143,7 @@ class Test_calendar(tests.IrisTest):
     def test_greg(self):
         field = DummyPPField()
         field.lbtim = SplittableInt(1, {"ia": 2, "ib": 1, "ic": 0})
-        self.assertEqual(field.calendar, "standard")
+        self.assertEqual(field.calendar, "proleptic_gregorian")
 
     def test_360(self):
         field = DummyPPField()