diff --git a/include/xlnt/workbook/workbook.hpp b/include/xlnt/workbook/workbook.hpp
index d4f00c06..33228910 100644
--- a/include/xlnt/workbook/workbook.hpp
+++ b/include/xlnt/workbook/workbook.hpp
@@ -827,6 +827,11 @@ private:
     /// </summary>
     void garbage_collect_formulae();
 
+    /// <summary>
+    /// Update extended workbook properties titlesOfParts and headingPairs when sheets change.
+    /// </summary>
+    void update_sheet_properties();
+
     /// <summary>
     /// An opaque pointer to a structure that holds all of the data relating to this workbook.
     /// </summary>
diff --git a/source/detail/xlsx_producer.cpp b/source/detail/xlsx_producer.cpp
index be65eb96..ac5c8ad1 100755
--- a/source/detail/xlsx_producer.cpp
+++ b/source/detail/xlsx_producer.cpp
@@ -252,6 +252,11 @@ void xlsx_producer::write_property(const std::string &name, const variant &value
             write_start_element(constants::ns("vt"), "lpwstr");
         }
 
+        if (!custom && ns == constants::ns("dcterms") && (name == "created" || name == "modified"))
+        {
+            write_attribute(xml::qname(constants::ns("xsi"), "type"), "dcterms:W3CDTF");
+        }
+
         write_characters(value.get<std::string>());
 
         if (custom)
diff --git a/source/workbook/tests/test_round_trip.hpp b/source/workbook/tests/test_round_trip.hpp
index d730a402..0c9086ed 100644
--- a/source/workbook/tests/test_round_trip.hpp
+++ b/source/workbook/tests/test_round_trip.hpp
@@ -24,6 +24,7 @@ public:
 
         std::vector<std::uint8_t> destination;
         source_workbook.save(destination);
+        source_workbook.save("temp.xlsx");
 
         std::ifstream source_stream(source.string(), std::ios::binary);
 
diff --git a/source/workbook/workbook.cpp b/source/workbook/workbook.cpp
index ed14078a..8b346759 100644
--- a/source/workbook/workbook.cpp
+++ b/source/workbook/workbook.cpp
@@ -759,6 +759,8 @@ worksheet workbook::create_sheet()
         workbook_rel.target(), relationship_type::worksheet, relative_sheet_uri, target_mode::internal);
     d_->sheet_title_rel_id_map_[title] = ws_rel;
 
+    update_sheet_properties();
+
     return worksheet(&d_->worksheets_.back());
 }
 
@@ -1007,9 +1009,10 @@ void workbook::remove_sheet(worksheet ws)
     }
 
     auto ws_rel_id = d_->sheet_title_rel_id_map_.at(ws.title());
-    auto wb_rel = d_->manifest_.relationship(xlnt::path("/"), xlnt::relationship_type::office_document);
+    auto wb_rel = d_->manifest_.relationship(path("/"), xlnt::relationship_type::office_document);
     auto ws_rel = d_->manifest_.relationship(wb_rel.target().path(), ws_rel_id);
-    d_->manifest_.unregister_override_type(ws_rel.target().path());
+    auto ws_part = d_->manifest_.canonicalize({wb_rel, ws_rel}).resolve(path("/"));
+    d_->manifest_.unregister_override_type(ws_part);
     auto rel_id_map = d_->manifest_.unregister_relationship(wb_rel.target(), ws_rel_id);
     d_->sheet_title_rel_id_map_.erase(ws.title());
     d_->worksheets_.erase(match_iter);
@@ -1020,6 +1023,8 @@ void workbook::remove_sheet(worksheet ws)
         title_rel_id_pair.second = rel_id_map.count(title_rel_id_pair.second) > 0
             ? rel_id_map[title_rel_id_pair.second] : title_rel_id_pair.second;
     }
+
+    update_sheet_properties();
 }
 
 worksheet workbook::create_sheet(std::size_t index)
@@ -1054,6 +1059,8 @@ worksheet workbook::create_sheet_with_rel(const std::string &title, const relati
         workbook_rel.target(), relationship_type::worksheet, rel.target(), target_mode::internal);
     d_->sheet_title_rel_id_map_[title] = ws_rel;
 
+    update_sheet_properties();
+
     return worksheet(&d_->worksheets_.back());
 }
 
@@ -1499,4 +1506,18 @@ void workbook::garbage_collect_formulae()
     }
 }
 
+void workbook::update_sheet_properties()
+{
+    if (has_extended_property(extended_property::titles_of_parts))
+    {
+        extended_property(extended_property::titles_of_parts, sheet_titles());
+    }
+
+    if (has_extended_property(extended_property::heading_pairs))
+    {
+        extended_property(extended_property::heading_pairs,
+            std::vector<variant>{variant("Worksheets"), variant(static_cast<int>(sheet_count()))});
+    }
+}
+
 } // namespace xlnt
diff --git a/source/worksheet/worksheet.cpp b/source/worksheet/worksheet.cpp
index 445de53a..1c8cb0f8 100644
--- a/source/worksheet/worksheet.cpp
+++ b/source/worksheet/worksheet.cpp
@@ -275,8 +275,8 @@ void worksheet::title(const std::string &title)
         throw invalid_sheet_title(title);
     }
 
-    auto same_title =
-        std::find_if(workbook().begin(), workbook().end(), [&](worksheet ws) { return ws.title() == title; });
+    auto same_title = std::find_if(workbook().begin(), workbook().end(),
+        [&](worksheet ws) { return ws.title() == title; });
 
     if (same_title != workbook().end() && *same_title != *this)
     {
@@ -286,6 +286,8 @@ void worksheet::title(const std::string &title)
     workbook().d_->sheet_title_rel_id_map_[title] = workbook().d_->sheet_title_rel_id_map_[d_->title_];
     workbook().d_->sheet_title_rel_id_map_.erase(d_->title_);
     d_->title_ = title;
+
+    workbook().update_sheet_properties();
 }
 
 cell_reference worksheet::frozen_panes() const