Q:

What time/day does voting for the first EOS election start?

When the EOS blockchain launches I read that the initial producers will be "self-appointed" and then the election process starts.
When does voting start and how long does it go on before the first elected block producers are known?

A:

There is no absolute answer for your question but here is some general advice (as taken from the community, not specifically my own)
After 5 or more Block Producer candidates declare publicly that the mainnet is ready for voting (and you should trust those BP candidates are authentic, honest, and have worked closely with the launch team, and support only one mainnet) ... then voting can start. 
Details on how to vote will be supplied by the BP candidates. As always please be careful and do not get scammed.
Once at least 15% of all votes are cast then those elected BPs run the mainnet. 
How long it takes depends on how quickly tokenholders vote.
Remember voting is a fluid process: the top 21 BP can change.
For anyone who is not completely sure of what to do: 
The safest course of action is to do nothing. You lose nothing by waiting a little longer and checking that all BPs are happy with the mainnet before participating. This advice was discussed on the EOS Launch Party.
Please read more here:
https://medium.com/@bensig/letter-to-eos-block-producer-candidates-184ef59a0748
https://steemit.com/eos/@eosdac/eos-mainnet-launch-the-order-of-events

