HM01 3-7-2021 at 22:10UTC

HM01 was first heard on 17 November 2012, initially on some of the V02a and M08a schedules that had existed at the time. The current HM01 schedule was developed starting in December 2012, and has not been changed since early 2015.
Until 1 November 2018, HM01 updated each of the six message slots on a daily basis, independently of each other. Each message usually spent 10 days on a slot. Typically, the age counter was set to 1 for the first two days, then incremented by one with each day, and the day after the counter reached 8, the message was replaced.
Since 1 November 2018, HM01 broadcasts sets of messages with unchanged age counters for prolonged periods of time, with the entire set being replaced when a need comes. Occasionally, HM01 returns to its old message rotating behavior, but only for a few days or weeks at a time.