I think we can say a minimum of 3 years. We've had at least two timeskips into "it's winter now" territory and I'm pretty sure there was a separate timeskip for "Faye gets buff at the robot fight club". My personal headcanon puts it at closer to 5-6 years to account for various people having relationships.


Meanwhile in Something Positive land we have the adopted daughter of two of the main characters having her first period. They got together years after the strip started and adopted said daughter as a baby. We've seen her grow older in roughly real time. It really puts into perspective how weird comic book time makes things.