Actually, permit applications can be submitted on March 1 (for 9-12 hikers) and on March 15 for 1 to 8 hikers. All of the applications received during the 24 hour period will be randomly selected and processed for permits. Any applications received after March 15 will be processed after all the other applications are completed, and then in order of receipt.
For a couple years, you were able to send the applications in during January. About 2 years ago, the Park went back to the one day window.
More details on the process can be found on the Glacier Park website -
https://www.nps.gov/glac/planyourvisit/ ... ations.htm