The key filing Dates for the Federal Individual Income Taxes are:

January 15th  4th Quarter Estimated Tax Due
April 15th  Individual Tax Returns due
April 15th  1st Quarter Estimated Tax due
June 15th  2nd Quarter Estimated Tax due
August 15th  Extension Filing due (1st Extension)
September 15th  3rd Quarter Estimated Tax due 

Please note: If the 15th falls on a weekend, the filing date moves to the
following Monday.