I came across the following issue with condition variables. I don't know if this is an issue with my application or with Boost condition variables. First my setup. I am using Linux on an ARM system, running Boost 1.47. My application needs accurate timing, and for this I use a POSIX timer using SIGRTMIN. This part is not something that I can control, it is an external library that implements this. I use condition variables are a timing mechanism with in my software. When I use condition variables without the POSIX timer there is no problem. The timing continues correctly, even if I change the time forward or backward. When I start the POSIX timer the condition variable does not time-out when I change the time backward. It only times out when the original time (plus timeout) is reached. The code I use to create the condition variable: boost::mutex m; boost::condition_variable cond; boost::unique_lock<boost::mutex> lk(m); cond.timed_wait(lk, duration); I tested this also by extracting the code from Boost and implementing this inline. This gave the same results. When I changed the clock of the pthread condition variable to monotonic (call to pthread_condattr_setclock(&condattr, CLOCK_MONOTONIC)) the result was OK again. Is this an issue with my implementation, can I change some setting or is this a (known) issue with the Boost condition variables? If people are interested, I do have a small test application that I used to test this issue that I can post here. I don't know however what the policy is on this list wrt posting of attachments. Kind regards, Johan Borkhuis