Here's a list of key dates and deadlines for tax season 2016-2017. 

2017 Deadline
Tax Related Activity
January 1, 2017 First day to file a 2016 tax return, though the IRS generally will not accept e-file and free file returns until the date below. Even paper based filings won't be processed till later in the month
January 23, 2017 IRS E-file to go live, allowing submission of electronic tax returns for the vast majority of tax filers. Paper tax returns will begin processing from this date as well
January 31, 2017 Date by which you should have received a W-2 from employers you worked for during the tax year. If not, contact their HR/Payroll department to resend tax documents
February 1, 2017 Deadline for 1099 statements (factors in your AGI income) that report non-employee compensation, bank interest, dividends and distributions from a retirement plan. This date is also the deadline for self-employed individuals to file and pay in full their fourth-quarter estimated tax payment
February 16, 2017 Financial institutions (e.g Vanguard, Fidelity) must mail out 1099-B, 1099-S and 1099-MISC forms by this date 
March 15, 2017 S Corporation and Partnership tax returns due
April 18, 2017 *Tax Day* Last day for filing federal income tax returns and extension requests. Since April 15th is a Saturday and Monday is the Emancipation Day holiday the due date has been shifted out to Tuesday, April 18th.
April 18, 2017 Deadline for filing state income tax returns (for most states) and extension requests. Last day to make a contribution to a Traditional or Roth IRA, Health Savings Account (HSA), SEP-IRA or 401(k)
June 15, 2017 U.S. citizens or resident aliens living abroad must file tax returns and pay any taxes due by this date (or file for a four-month extension)
June 30, 2017 FBAR (Foreign Bank Account Report) forms due for taxpayers who have over $10,000 in total in foreign bank accounts in the prior year. No extensions are allowed and forms must be filed electronically
October 15, 2017 Filing approved extended federal, state and S-Corp/Partnership income tax returns Note: you still need to file for an extension request by April 17th
April 15, 2020 Filing a 2016 tax amendment. You can file an amended or previous year return anytime, but you have a deadline of 3 years from the original due date to claim any tax refund