You can file in January. It typically takes six weeks before you get your return- but because of the recent tax 'revisions' if you get certain tax credits (college and teachers) or you do line item deductions then the IRS said it could take longer. For most people though that won't be the case.
You can file them as soon as January, the earlier you file the faster you get it back. If you file in January and do direct deposit you will get your refund within two weeks. If you file in april you might not get it for 6 weeks