diff --git a/std/datetime/date.d b/std/datetime/date.d
index c3ed199c6aa..fbe986a1b9f 100644
--- a/std/datetime/date.d
+++ b/std/datetime/date.d
@@ -3106,7 +3106,7 @@ public:
         import std.format : format;
         import std.string : strip;
 
-        immutable str = strip(isoString);
+        auto str = strip(isoString);
 
         enforce(str.length >= 15, new DateTimeException(format("Invalid ISO String: %s", isoString)));
         auto t = str.countUntil('T');
@@ -3172,6 +3172,18 @@ public:
         assert(DateTime.fromISOString(" 19990706T123033 ") == DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)));
     }
 
+    // bug# 17801
+    @safe unittest
+    {
+        import std.conv : to;
+        import std.meta : AliasSeq;
+        foreach (C; AliasSeq!(char, wchar, dchar))
+        {
+            foreach (S; AliasSeq!(C[], const(C)[], immutable(C)[]))
+                assert(DateTime.fromISOString(to!S("20121221T141516")) == DateTime(2012, 12, 21, 14, 15, 16));
+        }
+    }
+
 
     /++
         Creates a $(LREF DateTime) from a string with the format
@@ -3194,7 +3206,7 @@ public:
         import std.format : format;
         import std.string : strip;
 
-        immutable str = strip(isoExtString);
+        auto str = strip(isoExtString);
 
         enforce(str.length >= 15, new DateTimeException(format("Invalid ISO Extended String: %s", isoExtString)));
         auto t = str.countUntil('T');
@@ -3259,6 +3271,18 @@ public:
         assert(DateTime.fromISOExtString(" 1999-07-06T12:30:33 ") == DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)));
     }
 
+    // bug# 17801
+    @safe unittest
+    {
+        import std.conv : to;
+        import std.meta : AliasSeq;
+        foreach (C; AliasSeq!(char, wchar, dchar))
+        {
+            foreach (S; AliasSeq!(C[], const(C)[], immutable(C)[]))
+                assert(DateTime.fromISOExtString(to!S("2012-12-21T14:15:16")) == DateTime(2012, 12, 21, 14, 15, 16));
+        }
+    }
+
 
     /++
         Creates a $(LREF DateTime) from a string with the format
@@ -3281,7 +3305,7 @@ public:
         import std.format : format;
         import std.string : strip;
 
-        immutable str = strip(simpleString);
+        auto str = strip(simpleString);
 
         enforce(str.length >= 15, new DateTimeException(format("Invalid string format: %s", simpleString)));
         auto t = str.countUntil(' ');
@@ -3350,6 +3374,18 @@ public:
                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)));
     }
 
+    // bug# 17801
+    @safe unittest
+    {
+        import std.conv : to;
+        import std.meta : AliasSeq;
+        foreach (C; AliasSeq!(char, wchar, dchar))
+        {
+            foreach (S; AliasSeq!(C[], const(C)[], immutable(C)[]))
+                assert(DateTime.fromSimpleString(to!S("2012-Dec-21 14:15:16")) == DateTime(2012, 12, 21, 14, 15, 16));
+        }
+    }
+
 
     /++
         Returns the $(LREF DateTime) farthest in the past which is representable
@@ -7467,6 +7503,18 @@ public:
         assert(Date.fromISOString(" 19990706 ") == Date(1999, 7, 6));
     }
 
+    // bug# 17801
+    @safe unittest
+    {
+        import std.conv : to;
+        import std.meta : AliasSeq;
+        foreach (C; AliasSeq!(char, wchar, dchar))
+        {
+            foreach (S; AliasSeq!(C[], const(C)[], immutable(C)[]))
+                assert(Date.fromISOString(to!S("20121221")) == Date(2012, 12, 21));
+        }
+    }
+
 
     /++
         Creates a $(LREF Date) from a string with the format YYYY-MM-DD.
@@ -7596,6 +7644,18 @@ public:
         assert(Date.fromISOExtString(" 1999-07-06 ") == Date(1999, 7, 6));
     }
 
+    // bug# 17801
+    @safe unittest
+    {
+        import std.conv : to;
+        import std.meta : AliasSeq;
+        foreach (C; AliasSeq!(char, wchar, dchar))
+        {
+            foreach (S; AliasSeq!(C[], const(C)[], immutable(C)[]))
+                assert(Date.fromISOExtString(to!S("2012-12-21")) == Date(2012, 12, 21));
+        }
+    }
+
 
     /++
         Creates a $(LREF Date) from a string with the format YYYY-Mon-DD.
@@ -7722,6 +7782,18 @@ public:
         assert(Date.fromSimpleString(" 1999-Jul-06 ") == Date(1999, 7, 6));
     }
 
+    // bug# 17801
+    @safe unittest
+    {
+        import std.conv : to;
+        import std.meta : AliasSeq;
+        foreach (C; AliasSeq!(char, wchar, dchar))
+        {
+            foreach (S; AliasSeq!(C[], const(C)[], immutable(C)[]))
+                assert(Date.fromSimpleString(to!S("2012-Dec-21")) == Date(2012, 12, 21));
+        }
+    }
+
 
     /++
         Returns the $(LREF Date) farthest in the past which is representable by
@@ -8986,6 +9058,18 @@ public:
         assert(TimeOfDay.fromISOString(" 011217 ") == TimeOfDay(1, 12, 17));
     }
 
+    // bug# 17801
+    @safe unittest
+    {
+        import std.conv : to;
+        import std.meta : AliasSeq;
+        foreach (C; AliasSeq!(char, wchar, dchar))
+        {
+            foreach (S; AliasSeq!(C[], const(C)[], immutable(C)[]))
+                assert(TimeOfDay.fromISOString(to!S("141516")) == TimeOfDay(14, 15, 16));
+        }
+    }
+
 
     /++
         Creates a $(LREF TimeOfDay) from a string with the format HH:MM:SS.
@@ -9101,6 +9185,18 @@ public:
         assert(TimeOfDay.fromISOExtString(" 01:12:17 ") == TimeOfDay(1, 12, 17));
     }
 
+    // bug# 17801
+    @safe unittest
+    {
+        import std.conv : to;
+        import std.meta : AliasSeq;
+        foreach (C; AliasSeq!(char, wchar, dchar))
+        {
+            foreach (S; AliasSeq!(C[], const(C)[], immutable(C)[]))
+                assert(TimeOfDay.fromISOExtString(to!S("14:15:16")) == TimeOfDay(14, 15, 16));
+        }
+    }
+
 
     /++
         Returns midnight.
diff --git a/std/datetime/systime.d b/std/datetime/systime.d
index a4fc5b3201a..e0df970beda 100644
--- a/std/datetime/systime.d
+++ b/std/datetime/systime.d
@@ -8480,6 +8480,21 @@ public:
         test("20101222T172201.45+08:00", SysTime(DateTime(2010, 12, 22, 17, 22, 01), hnsecs(4_500_000), east480));
     }
 
+    // bug# 17801
+    @safe unittest
+    {
+        import std.conv : to;
+        import std.meta : AliasSeq;
+        foreach (C; AliasSeq!(char, wchar, dchar))
+        {
+            foreach (S; AliasSeq!(C[], const(C)[], immutable(C)[]))
+            {
+                assert(SysTime.fromISOString(to!S("20121221T141516Z")) ==
+                       SysTime(DateTime(2012, 12, 21, 14, 15, 16), UTC()));
+            }
+        }
+    }
+
 
     /++
         Creates a $(LREF SysTime) from a string with the format
@@ -8706,6 +8721,21 @@ public:
         test("2010-12-22T17:22:01.45+08:00", SysTime(DateTime(2010, 12, 22, 17, 22, 01), hnsecs(4_500_000), east480));
     }
 
+    // bug# 17801
+    @safe unittest
+    {
+        import std.conv : to;
+        import std.meta : AliasSeq;
+        foreach (C; AliasSeq!(char, wchar, dchar))
+        {
+            foreach (S; AliasSeq!(C[], const(C)[], immutable(C)[]))
+            {
+                assert(SysTime.fromISOExtString(to!S("2012-12-21T14:15:16Z")) ==
+                       SysTime(DateTime(2012, 12, 21, 14, 15, 16), UTC()));
+            }
+        }
+    }
+
 
     /++
         Creates a $(LREF SysTime) from a string with the format
@@ -8935,6 +8965,21 @@ public:
         test("2010-Dec-22 17:22:01.45+08:00", SysTime(DateTime(2010, 12, 22, 17, 22, 01), hnsecs(4_500_000), east480));
     }
 
+    // bug# 17801
+    @safe unittest
+    {
+        import std.conv : to;
+        import std.meta : AliasSeq;
+        foreach (C; AliasSeq!(char, wchar, dchar))
+        {
+            foreach (S; AliasSeq!(C[], const(C)[], immutable(C)[]))
+            {
+                assert(SysTime.fromSimpleString(to!S("2012-Dec-21 14:15:16Z")) ==
+                       SysTime(DateTime(2012, 12, 21, 14, 15, 16), UTC()));
+            }
+        }
+    }
+
 
     /++
         Returns the $(LREF SysTime) farthest in the past which is representable