--- a/mercurial/help/dates.txt	Mon Jan 28 12:19:21 2013 -0800
+++ b/mercurial/help/dates.txt	Wed Jan 23 09:51:45 2013 -0800
@@ -18,6 +18,8 @@
 - ``12-6``
 - ``12/6``
 - ``12/6/6`` (Dec 6 2006)
+- ``today`` (midnight)
+- ``yesterday`` (midnight)
 
 Lastly, there is Mercurial's internal format:
 

--- a/mercurial/util.py	Mon Jan 28 12:19:21 2013 -0800
+++ b/mercurial/util.py	Wed Jan 23 09:51:45 2013 -0800
@@ -1027,6 +1027,14 @@
 
     The date may be a "unixtime offset" string or in one of the specified
     formats. If the date already is a (unixtime, offset) tuple, it is returned.
+
+    >>> parsedate(' today ') == parsedate(\
+                                  datetime.date.today().strftime('%b %d'))
+    True
+    >>> parsedate( 'yesterday ') == parsedate((datetime.date.today() -\
+                                               datetime.timedelta(days=1)\
+                                              ).strftime('%b %d'))
+    True
     """
     if not date:
         return 0, 0
@@ -1035,6 +1043,13 @@
     if not formats:
         formats = defaultdateformats
     date = date.strip()
+
+    if date == _('today'):
+        date = datetime.date.today().strftime('%b %d')
+    elif date == _('yesterday'):
+        date = (datetime.date.today() -
+                datetime.timedelta(days=1)).strftime('%b %d')
+
     try:
         when, offset = map(int, date.split(' '))
     except ValueError:

--- a/tests/test-parse-date.t	Mon Jan 28 12:19:21 2013 -0800
+++ b/tests/test-parse-date.t	Wed Jan 23 09:51:45 2013 -0800
@@ -234,3 +234,20 @@
   Sat Apr 15 13:30:00 2006 +0000
   Wed Feb 01 13:00:30 2006 -0500
   Wed Feb 01 13:00:30 2006 +0000
+
+Test issue 3764 (interpreting 'today' and 'yesterday')
+  $ echo "hello" >> a
+  >>> import datetime
+  >>> today = datetime.date.today().strftime("%b %d")
+  >>> yesterday = (datetime.date.today() - datetime.timedelta(days=1)).strftime("%b %d")
+  >>> dates = open('dates', 'w')
+  >>> dates.write(today + '\n')
+  >>> dates.write(yesterday)
+  >>> dates.close()
+  $ hg ci -d "`sed -n '1p' dates`" -m "today is a good day to code"
+  $ hg log -d today --template '{desc}\n'
+  today is a good day to code
+  $ echo "goodbye" >> a
+  $ hg ci -d "`sed -n '2p' dates`" -m "the time traveler's code"
+  $ hg log -d yesterday --template '{desc}\n'
+  the time traveler's code