Scott Harrington correctly pointed out the following (from comments on
You're going to get complaints from more folks about changing this long-standing format, which happens to be the default if nothing is specified after the '%d'.
What I mean is, a lot of people have been getting the space separator, and they are not explicitly asking for ISO8601, and now they're going to start getting a 'T' separator.
Presence/absence of a space will affect anyone who slices up their log files using awk or cut with whitespace delimiters.
I suggest you introduce a new pattern named 'DEFAULT' (and which gets used by default):