guild market vote auto reseting

hi, how often is the guild market vote? is it every 28 days or 21 days,

anyway, it's now broken. Last time it renewed I placed my votes, and usually the vote stays until the next vote, but I looked yesterday and noticed all my votes had been removed/reset to 0 , so I re-voted yesterday. and guess what, i looked today and all my votes had once again been reset to 0 , so i re-voted again and noticed there is 1 day and 9 hours left till the next. I am now expecting to look again tomoro to see it reset to 0 again