#
#
# patch "dates.cc"
#  from [e5cbb5bfbaa5d6b82900a814d589065919a51a23]
#    to [f2cbec98589e45cd6f5cf8a1e7d69e6f54f8defd]
# 
# patch "dates.hh"
#  from [b1a386de6f39e217d0e5f9f1197c50968112dbd8]
#    to [96d6837b825444479af1813301dcd3216881167e]
#
============================================================
--- dates.cc	e5cbb5bfbaa5d6b82900a814d589065919a51a23
+++ dates.cc	f2cbec98589e45cd6f5cf8a1e7d69e6f54f8defd
@@ -459,6 +459,12 @@ date_t::operator -=(u64 const & other)
   return *this;
 }
 
+s64
+date_t::operator -(date_t const & other)
+{
+  return d - other.d;
+}
+
 #ifdef BUILD_UNIT_TESTS
 #include "unit_tests.hh"
 
@@ -744,6 +750,17 @@ UNIT_TEST(date, comparisons)
   v += 59000;
   UNIT_TEST_CHECK(v == date_t::from_string("9999-12-31T23:59:59"));
   UNIT_TEST_CHECK_THROW(v += 1000, std::logic_error);
+
+  // check date differences
+  UNIT_TEST_CHECK(date_t::from_string("2000-05-05T00:00:01") -
+                  date_t::from_string("2000-05-05T00:00:00")
+                  == 1000);
+  UNIT_TEST_CHECK(date_t::from_string("2000-05-05T00:00:01") -
+                  date_t::from_string("2000-05-05T00:00:02")
+                  == -1000);
+  UNIT_TEST_CHECK(date_t::from_string("2000-05-05T01:00:00") -
+                  date_t::from_string("2000-05-05T00:00:00")
+                  == 3600000);
 }
 
 #endif
============================================================
--- dates.hh	b1a386de6f39e217d0e5f9f1197c50968112dbd8
+++ dates.hh	96d6837b825444479af1813301dcd3216881167e
@@ -60,6 +60,9 @@ struct date_t
   date_t & operator +=(u64 const & addend);
   date_t & operator -=(u64 const & addend);
 
+  // Difference between two dates in milliseconds
+  s64 operator -(date_t const & other);
+
 private:
   // The date as an unsigned 64-bit count of milliseconds since
   // the Unix epoch (1970-01-01T00:00:00.000).