SimpleDateFormat thread safety

[seancarroll]

PropertiesManager.java uses a private static SimpleDateFormat which is not thread safe. From the javadocs (http://docs.oracle.com/javase/6/docs/api/java/text/SimpleDateFormat.html)

Synchronization
Date formats are not synchronized. It is recommended to create separate format instances for each thread. If multiple threads access a format concurrently, it must be synchronized externally.

I can submit a PR just wondering what your preferred solution is

• Using instance variables
• Synchonization
• ThreadLocal

[rladines]

@seancarroll I see that the today and yesterday methods of PropertiesManager that use the SimpleDateFormat static are not being called anywhere at the moment. That does not mean we should not fix it though. Feel free to submit a pull request.

I think we can just go with the simpler option which is to use instance variables.