Add test files for PR 1999 / issue 1998

Author: jim-easterbrook

test/data/issue_1998.xmp

@@ -0,0 +1,9 @@
+<?xpacket begin="" id="W5M0MpCehiHzreSzNTczkc9d"?>
+<x:xmpmeta xmlns:x="adobe:ns:meta/" x:xmptk="XMP Core 4.4.0-Exiv2">
+ <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
+  <rdf:Description rdf:about=""
+    xmlns:xmp="http://ns.adobe.com/xap/1.0/"
+   xmp:CreateDate="2021-02-03T12:34:56+02:00"/>
+ </rdf:RDF>
+</x:xmpmeta>
+<?xpacket end="w"?>

tests/bugfixes/github/test_pr_1999.py

@@ -0,0 +1,28 @@
+# -*- coding: utf-8 -*-
+
+import system_tests
+from system_tests import CaseMeta, path
+
+class TestXmpDateTimeSetting(metaclass=CaseMeta):
+    """
+    Test fix for issue 1998.
+    """
+
+    infile = path("$data_path/issue_1998.xmp")
+    commands = [
+        "$exiv2 -M'set Xmp.xmp.CreateDate XmpText 2021-02-03T12:00:00+01:00' $infile",
+        "$exiv2 -K Xmp.xmp.CreateDate $infile",
+        "$exiv2 -M'set Xmp.xmp.CreateDate XmpText 2021-02-03T12:34:56+02:00' $infile",
+        "$exiv2 -K Xmp.xmp.CreateDate $infile",
+        ]
+    stdout = [
+        """""",
+        """Xmp.xmp.CreateDate                           XmpText    25  2021-02-03T12:00:00+01:00
+""",
+        """""",
+        """Xmp.xmp.CreateDate                           XmpText    25  2021-02-03T12:34:56+02:00
+""",
+              ]
+    stderr = [""]*4
+    retval = [0]*4
+