There still appears to be a problem with the data for Dec, 2015... the following query returns zero results as of now: http://api.fda.gov/device/event.json?search=date_received:[20151201+TO+20151231]
The data that powers that particular API is only available on a quarterly basis and is currently only available through Q3 of 2015.
Even though the data is released on a quarterly basis, the pipeline that updates the
/drug/event.json endpoint is run on a weekly basis in order to update the
openfda section of all the documents, since the
openfda section's data sources update cycles are more frequent.
Please let me know if you have any questions. Thanks for you using the openFDA.