Resolution:
TIBCO InegrationManager (TM) provides a property (advanced) under  "AETracing" tab of the property editor – “Format for timestamp". It can take any legal datetime pattern that is accepted by java.text.SimpleDateFormat(String pattern) constructor as its value. When an invalid pattern is passed to it, it gets defaulted to "yyyy MM dd hh:mm:ss:SSS"

So to change it to a 24-hour format you can use the following format – "yyyy MM dd HH:mm:ss:SSS"