fix typo

Author: coke

doc/Type/DateTime.pod6

@@ -103,7 +103,7 @@ Defined as:
 
 Creates a new C<DateTime> object from the current system time. A custom
 L<formatter> and L<timezone> can be provided. The C<:$timezone> is
-the offset B<in seconds> from L<GTM|https://en.wikipedia.org/wiki/Greenwich_Mean_Time>
+the offset B<in seconds> from L<GMT|https://en.wikipedia.org/wiki/Greenwich_Mean_Time>
 and defaults to the value of L«C<$*TZ> variable|/language/variables#index-entry-%24*TZ».
 
     say DateTime.now;