score:9
As far as we can tell, Christian twice-weekly fasting was based on Jewish twice-weekly fasting. Given the later tension between Jews and Christians, this makes an early adoption date likely.
Further evidence comes from the Didache (dating probably to the first century):
Your fasts should not be with the hypocrites, for they fast on Mondays and Thursdays. You should fast on Wednesdays and Fridays. (8.1)
This passage seems to indicate that a formal twice-weekly fast was the normβa practice which appears to be analogous to (but distinct from) the Jewish practice.