A caveat here as well is you also need to make sure your various clocks in the data center are synched. This is one of those common but overlooked scenarios which lead to hilarious discussions about latency when really there was just a clock synch problem. Additionally the fallacies of distributed computing come into play here (namely, transport cost is 0) so you need to take extra care when looking at measurements across different systems and machines. Even machines in the same data center. The pipe that you are communicating across could be oversubscribed for example.
UTC is not only unambiguous, but on some systems measurably faster to capture.
My experience has taught me to work in UTC everywhere possible, local time is typically only relevant for direct human interaction.