Timeline

Information regarding the actual date is vague, but a relatively accurate timeline of events is possible.

Overarching Timeline
The "Assumed Year" is based on episode Earth Kills's shown FIFA game occurring in late 2013 or early 2014. This fits well enough, but is not 100% certain.

Contemporary Timeline
The day that "The 100" were sent to Earth is considered day 1 of this calender and dates will proceed as 1.1.1 RY = Day 1, Month 1, Year 1 of Recolonization (R of the RY). BRY will be for dates previous to that day. When the show says "1 year ago" it will be assumed it was 365 days before the events being shown unless it can be understood that the event happens before/after an already known event.