I was slightly confused just because I skipped the "11:59" note at first, but once you see that there's really only one way it would make sense so I interpreted it that way. But if you want it to be uber clear you could try this:
DATES: Subject to change

*** ALL DEADLINES ARE AT 11:59pm EASTERN STANDARD TIME OF THE DAY LISTED ***

Round 1
Start: Wednesday, March 5th
Images due: Monday, March 10th, 11:59pm EST
Voting Starts: Tuesday, March 11th - after images are collected and posted
Voting ends: Wednesday, March 12, 11:59pm EST

Round 2:
Start: Wednesday, March 12th
Images due: Monday, March 17, 11:59pm EST
Voting Starts: Tuesday, March 18 - after images are collected and posted
Voting ends: Wednesday, March 19, 11:59pm EST

Round 3:
Start: Wednesday, March 19
Images due: Monday, March 24, 11:59pm EST
Voting Starts: Tuesday, March 25 - after images are collected and posted
Voting ends: Wednesday, March 26, 11:59pm EST

Round 4:
Start: Wednesday, March 26
Images due: Wednesday 11:59pm EST, April 2nd
Voting Starts: Thursday, April 3rd - after images are collected and posted
Voting Ends/WINNER ANNOUNCED: Saturday, April 5th, 11:59pm EST
No room for confusion there, I think.

Thanks for organizing this, lefteye, I was going to mention earlier I think you're doing a great job at getting and keeping this rolling really well. Keep up the good work.

Who are we waiting on at this point?