[dates] provide a somewhat reasonable workaround for ticks2datetime where year < 1900

2 files changed, 23 insertions, 3 deletions

diff --git a/date.py b/date.py
index 6fa470d..16d76f0 100644
--- a/date.py
+++ b/date.py
@@ -235,6 +235,19 @@ def todatetime(somedate):
 def datetime2ticks(somedate):
     return timegm(somedate.timetuple()) * 1000
 
+def ticks2datetime(ticks):
+    miliseconds, microseconds = divmod(ticks, 1000)
+    try:
+        return datetime.fromtimestamp(miliseconds)
+    except (ValueError, OverflowError):
+        epoch = datetime.fromtimestamp(0)
+        nb_days, seconds = divmod(int(miliseconds), 86400)
+        delta = timedelta(nb_days, seconds=seconds, microseconds=microseconds)
+        try:
+            return epoch + delta
+        except (ValueError, OverflowError):
+            raise
+
 def days_in_month(somedate):
     return monthrange(somedate.year, somedate.month)[1]
 
@@ -273,7 +286,7 @@ def ustrftime(somedate, fmt='%Y-%m-%d'):
     try:
         return unicode(somedate.strftime(str(fmt)), encoding)
     except ValueError, exc:
-        if '1900' not in exc.args[0]:
+        if somedate.year >= 1900:
             raise
         # datetime is not happy with dates before 1900
         # we try to work around this, assuming a simple
diff --git a/test/unittest_date.py b/test/unittest_date.py
index 701a473..e05df34 100644
--- a/test/unittest_date.py
+++ b/test/unittest_date.py
@@ -18,11 +18,11 @@
 """
 Unittests for date helpers
 """
-from logilab.common.testlib import TestCase, unittest_main
+from logilab.common.testlib import TestCase, unittest_main, tag
 
 from logilab.common.date import date_range, endOfMonth
 from logilab.common.date import add_days_worked, nb_open_days, \
-         get_national_holidays, ustrftime
+         get_national_holidays, ustrftime, ticks2datetime
 
 from datetime import date, datetime, timedelta
 
@@ -127,10 +127,17 @@ class DateTC(TestCase):
     def test_open_days_afternoon(self):
         self.assertOpenDays(self.datetimecls(2008, 5, 6, 14), self.datetimecls(2008, 5, 7, 14), 1)
 
+    @tag('posix', '1900')
     def test_ustrftime_before_1900(self):
         date = self.datetimecls(1328, 3, 12, 6, 30)
         self.assertEqual(ustrftime(date, '%Y-%m-%d %H:%M:%S'), u'1328-03-12 06:30:00')
 
+    @tag('posix', '1900')
+    def test_ticks2datetime_before_1900(self):
+        ticks = -2209075200000
+        date = ticks2datetime(ticks)
+        self.assertEqual(ustrftime(date, '%Y-%m-%d'), u'1899-12-31')
+
 
 class MxDateTC(DateTC):
     datecls = mxDate