Which seeds are used for native random number generators in common languages?

I am interested in finding out which seeds are used for native random number generators in common languages. Primarily, it's Javascript, Objective C, Swift and Android.

If you want to generate unique ids in distributed systems, you want to minimise the risk of collision. One strategy is to use a UNIX timestamp concatenated with a random number. However, if UNIX timestamp is also used as the sole seed for the random number generator, there is no point in adding a random number to the timestamp. If two units calculated an id at the same time using the same pseudo-random generator, they would then return the same random number as well. Using a hardware-specific id as part of the seed would be a good strategy, I think. But how is it actually implemented already in these languages?