If you will be out of the country, you get an automatic 2 month extension to June 15, but to obtain this extension without having first applied for the standard extension, you must file by mail and attach a written explanation.
The best thing to do, even if you will be out of the country, will be to either e-file the extension using Turbotax online (free, usually available in March, access from any computer with a web browser or a phone app, does not lock you into filing with Turbotax); or find someplace to download, print and mail the paper form in January. Just put a reminder in your calendar.
Note that if you need to file a form 1065 for a partnership or multi-member LLC, the deadline is March 15 and you will need to apply for a separate extension from your personal return.
