Fix time-string format in backend for GncDateTime(std::string).

Also provide a simple test of that ctor.

libgnucash/backend/sql/gnc-sql-column-table-entry.cpp

@@ -393,7 +393,13 @@ GncSqlColumnTableEntryImpl<CT_TIMESPEC>::load (const GncSqlBackend* sql_be,
     {
         try
         {
+            constexpr size_t datelen = 14;
             auto val = row.get_string_at_col(m_col_name);
+            if (val.length() == datelen)
+                val = std::string(val.substr(0, 4) + "-" + val.substr(4, 2) +
+                                  "-" + val.substr(6, 2) + " " +
+                                  val.substr(8, 2) + ":" + val.substr(10, 2) +
+                                  ":" + val.substr(12, 2));
             GncDateTime time(val);
             ts.tv_sec = static_cast<time64>(time);
         }

libgnucash/engine/test/gtest-gnc-datetime.cpp

@@ -259,6 +259,19 @@ TEST(gnc_datetime_constructors, test_time64_constructor)
     EXPECT_EQ(static_cast<time64>(atime), time);
 }
 
+TEST(gnc_datetime_constructors, test_string_constructor)
+{
+    std::string timestr("2015-12-05 00:01:00");
+    GncDateTime time(timestr);
+    auto tm = time.utc_tm();
+    EXPECT_EQ(tm.tm_year, 115);
+    EXPECT_EQ(tm.tm_mon, 11);
+    EXPECT_EQ(tm.tm_mday, 5);
+    EXPECT_EQ(tm.tm_hour, 0);
+    EXPECT_EQ(tm.tm_min, 1);
+    EXPECT_EQ(tm.tm_sec, 0);
+}
+
 TEST(gnc_datetime_constructors, test_struct_tm_constructor)
 {
 #ifdef HAVE_STRUCT_TM_GMTOFF