METRO
Metro works well, but this is the new version : https://github.com/SofaPirate/Chrono
Metro library for Arduino or Wiring that facilitates the implementation of recurring timed events by Thomas Ouellet Fredericks with contributions from: Paul Bouchier and Benjamin.soelberg
Download the latest version here : https://github.com/thomasfredericks/Metro-Arduino-Wiring/archive/master.zip
Documentation can be found here : https://github.com/thomasfredericks/Metro-Arduino-Wiring/wiki