Sets the timestamp format prepended by the default log targets to all
messages. The string may contain any normal characters as well as \%
prefixed format specificators, see {\it strftime()} manual for details.
-Passing a null value (not empty string) to this function disables message timestamping.
+Passing a NULL value (not empty string) to this function disables message timestamping.
\membersection{wxLog::GetTimestamp}\label{wxloggettimestamp}