diff --git a/CHANGELOG b/CHANGELOG
index 82b17fa36b..7ba3991bff 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,3 +1,5 @@
+* Use fixed year of 365 days
+
 Version 5.4.0 - 2019-11-04
 * Bug fixes (see mercurial logs for details)
 * Add depreciated amount
diff --git a/asset.py b/asset.py
index 0459560338..44e391ae1c 100644
--- a/asset.py
+++ b/asset.py
@@ -30,6 +30,26 @@ def date2datetime(date):
     return datetime.datetime.combine(date, datetime.time())
 
 
+February = 2
+
+
+def normalized_delta(start, end):
+    "Returns timedelta using fixed 365 days per year"
+    assert start <= end
+    delta = end - start
+    correction = 0
+    if start.year == end.year:
+        if calendar.isleap(start.year) and start.month <= 2 and end.month > 2:
+            correction -= 1
+    else:
+        if calendar.isleap(start.year) and start.month <= February:
+            correction -= 1
+        if calendar.isleap(end.year) and end.month > February:
+            correction -= 1
+        correction -= calendar.leapdays(start.year + 1, end.year)
+    return delta + datetime.timedelta(days=correction)
+
+
 class Asset(Workflow, ModelSQL, ModelView):
     'Asset'
     __name__ = 'account.asset'
@@ -396,21 +416,30 @@ class Asset(Workflow, ModelSQL, ModelView):
             start_date = max([self.start_date
                     - relativedelta.relativedelta(days=1)]
                 + [l.date for l in self.lines])
-            first_delta = dates[0] - start_date
+            first_delta = normalized_delta(start_date, dates[0])
             if len(dates) > 1:
-                last_delta = dates[-1] - dates[-2]
+                last_delta = normalized_delta(dates[-2], dates[-1])
             else:
                 last_delta = first_delta
             if self.frequency == 'monthly':
                 _, first_ndays = calendar.monthrange(
                     dates[0].year, dates[0].month)
+                if (calendar.isleap(dates[0].year)
+                        and dates[0].month == February):
+                    first_ndays -= 1
                 _, last_ndays = calendar.monthrange(
                     dates[-1].year, dates[-1].month)
+                if (calendar.isleap(dates[-1].year)
+                        and dates[-1].month == February):
+                    last_ndays -= 1
             elif self.frequency == 'yearly':
-                first_ndays = 365 + calendar.isleap(dates[0].year)
-                last_ndays = 365 + calendar.isleap(dates[-1].year)
-            first_ratio = Decimal(first_delta.days) / Decimal(first_ndays)
-            last_ratio = Decimal(last_delta.days) / Decimal(last_ndays)
+                first_ndays = last_ndays = 365
+            first_ratio = (
+                Decimal(min(first_delta.days, first_ndays))
+                / Decimal(first_ndays))
+            last_ratio = (
+                Decimal(min(last_delta.days, last_ndays))
+                / Decimal(last_ndays))
             depreciation = amount / (
                 len(dates) - 2 + first_ratio + last_ratio)
             if date == dates[0]:
diff --git a/doc/index.rst b/doc/index.rst
index a8c9ed03b0..a46afd95f7 100644
--- a/doc/index.rst
+++ b/doc/index.rst
@@ -13,10 +13,14 @@ An Asset defines how an asset is depreciated. It is mainly defined by:
 - Value, Depreciated Amount and Residual Value.
 - Start and End Date.
 - Depreciation Method:
+
   - Linear
+
 - Frequency:
+
   - Monthly
-  - Yearly
+  - Yearly (using fixed year of 365 days)
+
 - Lines.
 
 The asset can be in one of this states:
@@ -31,7 +35,7 @@ The asset can be in one of this states:
 
 * Closed
 
-  The value of the asset has been completly depreciated.
+  The value of the asset has been completely depreciated.
 
 A wizard "Create Assets Moves" allows to post all accounting move up to a date.
 
diff --git a/tests/test_account_asset.py b/tests/test_account_asset.py
index 97ea9f9d5e..63e3758d69 100644
--- a/tests/test_account_asset.py
+++ b/tests/test_account_asset.py
@@ -1,5 +1,6 @@
 # This file is part of Tryton.  The COPYRIGHT file at the top level of
 # this repository contains the full copyright notices and license terms.
+import datetime as dt
 import unittest
 import doctest
 import trytond.tests.test_tryton
@@ -7,12 +8,40 @@ from trytond.tests.test_tryton import ModuleTestCase
 from trytond.tests.test_tryton import doctest_teardown
 from trytond.tests.test_tryton import doctest_checker
 
+from trytond.modules.account_asset.asset import normalized_delta
+
 
 class AccountAssetTestCase(ModuleTestCase):
     'Test AccountAsset module'
     module = 'account_asset'
     extras = ['purchase']
 
+    def test_normalized_delta(self):
+        "Test normalized detal"
+        for start, end, delta in [
+                (dt.date(2019, 1, 1), dt.date(2019, 12, 31),
+                    dt.timedelta(days=364)),
+                (dt.date(2019, 1, 1), dt.date(2020, 1, 1),
+                    dt.timedelta(days=365)),
+                (dt.date(2019, 1, 1), dt.date(2019, 3, 1),
+                    dt.timedelta(days=31 + 28)),
+                (dt.date(2024, 1, 1), dt.date(2024, 2, 1),
+                    dt.timedelta(days=31)),
+                (dt.date(2024, 1, 1), dt.date(2024, 3, 1),
+                    dt.timedelta(days=31 + 28)),
+                (dt.date(2024, 3, 1), dt.date(2024, 4, 1),
+                    dt.timedelta(days=31)),
+                (dt.date(2024, 1, 1), dt.date(2025, 1, 1),
+                    dt.timedelta(days=365)),
+                (dt.date(2023, 1, 1), dt.date(2025, 1, 1),
+                    dt.timedelta(days=365 * 2)),
+                (dt.date(2000, 1, 1), dt.date(2020, 1, 1),
+                    dt.timedelta(days=365 * 20)),
+                ]:
+            self.assertEqual(
+                normalized_delta(start, end), delta,
+                msg='%s - %s' % (start, end))
+
 
 def suite():
     suite = trytond.tests.test_tryton.suite()