I've got another suggestion based on the time zones:
According to the map from Civil War, Wakanda is between Uganda, Kenya, South Sudan and Ethiopia.
This means it is around 11 hours ahead of California.
As shown in Black Panther Prelude 1, the "I am Iron Man" press conference took place a few hours before the beginning of the comic. Said press conference took place in broad daylight (in California local time).
Due to the time difference between California and Wakanda, plus the few hours since the press conference, there's a gap of at least 13 hours (based on the local time of both), meaning Black Panther Prelude 1 likely starts the following morning.
When T'Challa in in Congo, the sky appears an orange tint (meaning it could be early morning), while when he arrives at Wakanda, the sky is blue (meaning daytime), which I believe backs me up.
So I'm thinking:
2008:
May 25:
-Daytime (California): "I am Iron Man"
May 26:
-Early morning (Congo): Events in Congo.
-Morning (Wakanda): T'Challa returns to Wakanda.
Does this make sense?