diff --git a/Makefile b/Makefile
index 70d4f44..854094f 100644
--- a/Makefile
+++ b/Makefile
@@ -68,7 +68,7 @@ excel-reader-xlsx:
 .PHONY: openpyxl
 openpyxl:
 	if [ ! -e openpyxl ]; then hg clone https://bitbucket.org/ericgazoni/openpyxl; fi
-	cd openpyxl; hg pull || echo foo
+	cd openpyxl; hg pull && hg update || echo foo
 	cd openpyxl/openpyxl/tests/test_data/genuine; for i in *.xls*; do cp $$i ../../../../../openpyxl_g_$$i; done
 	cd openpyxl/openpyxl/tests/test_data/reader; for i in *.xls*; do cp $$i ../../../../../openpyxl_r_$$i; done
 
diff --git a/number_format.xls.xml b/number_format.xls.xml
index e349d03..d5ada97 100644
--- a/number_format.xls.xml
+++ b/number_format.xls.xml
@@ -520,7 +520,7 @@
    <Row>
     <Cell><Data ss:Type="Number">14</Data></Cell>
     <Cell ss:StyleID="s74"><Data ss:Type="DateTime">1933-10-18T16:17:36.960</Data></Cell>
-    <Cell ss:Formula="=NumFmt(RC[-1])"><Data ss:Type="String">m/d/yyyy</Data></Cell>
+    <Cell ss:Formula="=NumFmt(RC[-1])"><Data ss:Type="String">m/d/yy</Data></Cell>
     <Cell ss:Formula="=Dofmt(RC[-2],RC[1])"><Data ss:Type="String">10/18/33</Data></Cell>
     <Cell><Data ss:Type="String" x:Ticked="1">m/d/yy</Data></Cell>
     <Cell ss:StyleID="s74" ss:Formula="=RC[-4]"><Data ss:Type="DateTime">1933-10-18T16:17:36.960</Data></Cell>
@@ -775,7 +775,7 @@
    <Row>
     <Cell><Data ss:Type="Number">14</Data></Cell>
     <Cell ss:StyleID="s74"><Data ss:Type="DateTime">1866-03-13T07:42:23.040</Data></Cell>
-    <Cell ss:Formula="=NumFmt(RC[-1])"><Data ss:Type="String">m/d/yyyy</Data></Cell>
+    <Cell ss:Formula="=NumFmt(RC[-1])"><Data ss:Type="String">m/d/yy</Data></Cell>
     <Cell ss:Formula="=Dofmt(RC[-2],RC[1])"><Data ss:Type="String">3/13/66</Data></Cell>
     <Cell><Data ss:Type="String" x:Ticked="1">m/d/yy</Data></Cell>
     <Cell ss:Formula="=RC[-1]=RC[-3]"><Data ss:Type="Boolean">0</Data></Cell>
diff --git a/number_format.xlsb.xml b/number_format.xlsb.xml
index 6213b5b..0c7e59f 100644
--- a/number_format.xlsb.xml
+++ b/number_format.xlsb.xml
@@ -409,7 +409,7 @@
    <Row>
     <Cell><Data ss:Type="Number">14</Data></Cell>
     <Cell ss:StyleID="s54"><Data ss:Type="DateTime">1933-10-18T16:17:36.960</Data></Cell>
-    <Cell ss:Formula="=NumFmt(RC[-1])"><Data ss:Type="String">m/d/yyyy</Data></Cell>
+    <Cell ss:Formula="=NumFmt(RC[-1])"><Data ss:Type="String">m/d/yy</Data></Cell>
     <Cell ss:Formula="=Dofmt(RC[-2],RC[1])"><Data ss:Type="String">10/18/33</Data></Cell>
     <Cell><Data ss:Type="String" x:Ticked="1">m/d/yy</Data></Cell>
     <Cell ss:StyleID="s54" ss:Formula="=RC[-4]"><Data ss:Type="DateTime">1933-10-18T16:17:36.960</Data></Cell>
@@ -662,7 +662,7 @@
    <Row>
     <Cell><Data ss:Type="Number">14</Data></Cell>
     <Cell ss:StyleID="s54"><Data ss:Type="DateTime">1866-03-13T07:42:23.040</Data></Cell>
-    <Cell ss:Formula="=NumFmt(RC[-1])"><Data ss:Type="String">m/d/yyyy</Data></Cell>
+    <Cell ss:Formula="=NumFmt(RC[-1])"><Data ss:Type="String">m/d/yy</Data></Cell>
     <Cell ss:Formula="=Dofmt(RC[-2],RC[1])"><Data ss:Type="String">3/13/66</Data></Cell>
     <Cell><Data ss:Type="String" x:Ticked="1">m/d/yy</Data></Cell>
     <Cell ss:Formula="=RC[-1]=RC[-3]"><Data ss:Type="Boolean">0</Data></Cell>
diff --git a/number_format.xlsm.xml b/number_format.xlsm.xml
index 4f1b847..3791530 100644
--- a/number_format.xlsm.xml
+++ b/number_format.xlsm.xml
@@ -409,7 +409,7 @@
    <Row>
     <Cell><Data ss:Type="Number">14</Data></Cell>
     <Cell ss:StyleID="s54"><Data ss:Type="DateTime">1933-10-18T16:17:36.960</Data></Cell>
-    <Cell ss:Formula="=NumFmt(RC[-1])"><Data ss:Type="String">m/d/yyyy</Data></Cell>
+    <Cell ss:Formula="=NumFmt(RC[-1])"><Data ss:Type="String">m/d/yy</Data></Cell>
     <Cell ss:Formula="=Dofmt(RC[-2],RC[1])"><Data ss:Type="String">10/18/33</Data></Cell>
     <Cell><Data ss:Type="String" x:Ticked="1">m/d/yy</Data></Cell>
     <Cell ss:StyleID="s54" ss:Formula="=RC[-4]"><Data ss:Type="DateTime">1933-10-18T16:17:36.960</Data></Cell>
@@ -662,7 +662,7 @@
    <Row>
     <Cell><Data ss:Type="Number">14</Data></Cell>
     <Cell ss:StyleID="s54"><Data ss:Type="DateTime">1866-03-13T07:42:23.040</Data></Cell>
-    <Cell ss:Formula="=NumFmt(RC[-1])"><Data ss:Type="String">m/d/yyyy</Data></Cell>
+    <Cell ss:Formula="=NumFmt(RC[-1])"><Data ss:Type="String">m/d/yy</Data></Cell>
     <Cell ss:Formula="=Dofmt(RC[-2],RC[1])"><Data ss:Type="String">3/13/66</Data></Cell>
     <Cell><Data ss:Type="String" x:Ticked="1">m/d/yy</Data></Cell>
     <Cell ss:Formula="=RC[-1]=RC[-3]"><Data ss:Type="Boolean">0</Data></Cell>