UTC is great for timestamps, but he needs to make his times sortable (YYYY-MM-DD) Tab delimited fields are a problem, unless you escape the tabs inside the data you log.

This format seems VERY similar to the Graylog Extended Log Format (or GELF) https://github.com/Graylog2/graylog2-docs/wiki/GELF

I'm a huge fan of JSON logs now, having just finished implementing them on a major work project. Every language out there can take JSON in and do work against it, and there are some really awesome tools for rendering filtered logs to a browser in realtime.