No Start-Time for milestones in GitHub

In GitHub, you cannot specify a start time for milestones. The calculation that the start time of the milestone takes over the end of the last milestone only works for consecutive milestones (we use milestones as project phases, which is actually not entirely correct from a project management perspective as a milestone describes the end of a project phase). This system does not work for phases running in parallel. I think we have two options: we put a comment in the milestone [start time dd.mm.yyyy hh:mm] or we switch to GitHub projects in which we can specify the start and end time of tickets using fields, so the project or phase duration can be derived from the earliest start and latest end of a ticket