Atlas publishes “30 Day” and “60 Day” lines which are really one and two month lines except January and March each give February a day to make all three months 30 days. It’s random how many are 30 day and how many are 60 day. The bid packs go out at 17:00 Z on the 18th and bidding closes at 17:00 Z on the 21st. There will be some number of VTO (Vacation, Training and Other) lines in the bid. Awards are required to be published by 17:00 Z on the 23rd however they’ve been getting them out late on the 21st recently. If you got a VTO line there will be another set of lines posted at 17:00 Z on 24th with bidding open for 24 hours. The final award is posted by 23:59 on the 27th.
Polar only has its Chief Pilot to keep the certificate alive so there is no separate bidding for Polar flights.