At 9:00am PDT Bittrex closed the market for ZCL in preparation for the ZEN fork.
Note: Bittrex will be closing our ZCL wallet and market within two hours of the fork block to take accurate snapshots of balances. If your deposits are not settled (e.g. marked as pending) by 09:00 PDT 5/18/2017, you may not be credited with ZEN.
The block height at this time is 109877, it'll take another 123 blocks before we get to 110,000. That means roughly 6 hours (123 blks / 24 blks/hr = 5.125hr).
If the block 110,000 is mined around 3:00pm and we add the two hours needed for Bittrex to take snapshots, we can conclude that the market will open at the very earliest around 5:00pm PDT.