As described here:
https://github.com/salesagility/SuiteCRM/issues/3315
I strongly suggest to add the date field that permit to change the time of the email queue while mass updating.
Today I have mass updated some emails i nthe queue, they was planned for today at time 16:00 and then I updated that queue for the same day, but the time changed by itself to 00:00, so then I discovered that it is missing the time field in the mass update and I suggest to add it to the next release, here the screenshot to explain it better