STS-134 8:56 a.m. EDT on Monday, May 16.

NASA managers have set the liftoff of space shuttle Endeavour for 8:56 a.m. EDT on Monday, May 16.
AMS-02 - swissinfo
http://www.swissinfo.ch/jpn/detail/content.html?cid=30150450

5/16 -- STS-134/Endeavour launch ULF6 (ELC-3, AMS) ~8:56am EDT [not earlier than]
5/18-- STS-134/Endeavour docking – for a 16-day mission
5/23/-- Soyuz TMA-20/25S undock/landing (End of Increment 27)
Three-crew operations
6/07 -- Soyuz TMA-02M/27S launch – M. Fossum (CDR-29)/S. Furukawa/S. Volkov