Also, I believe it takes about 30 days for the government to notify TSP you retired. You won't be able to take funds out until TSP is notified of your retirement. If you are working until mid January the withdrawal
request for Jan 2 would be considered an in-service withdrawal. See below from TSP Website.
If you retire when your eligible, Dec 13, about mid January you'd be able to submit a withdrawal request, and the funds would be on the 2014 tax year. https://www.tsp.gov/planparticipatio...gAccount.shtml
Consequences of Age-Based Withdrawals
Your age-based withdrawal is subject to Federal income tax and, in some cases, state income tax. Any tax-exempt or Roth contributions included in your withdrawal are not subject to Federal income tax; neither are any qualified Roth earnings.
If you make an age-based withdrawal, you will not be eligible to receive a partial withdrawal from the same account after you separate from service.