Games : What is the logic behind the timer of the Sojourner Badge?

Does the 24 hours timer start:

• when you hack a portal on a particular day

or

• does it use the calendar days and check if you did hack a portal on a particular day

or

• does it simply use a fixed international timezone to calculate the 24 hour cycle

or

• does it use the agent's hacking cell's timezone to start it?

If it's the calendar days method than the explanation of the badge would be a little bit misguided because you could hack a portal on 00:01 on Saturday and then hack another one on 23:59 on Sunday and it would be practically two days between two hacks.

If it's based on the agent's last hack for a particular day then the explanation still would be problematic?

The third option would be a little bit unfair (or timezone racist) for the rest of the world.

The last ption (the cell's timezone) would/could be both unfair for travellers and/or non-travellers.

Does anyone know any details about it?