Calculating number of payments on BTCJam

[Gidik]

Hi guys. I have some hard time trying to figure out something about BTCJam. Let’s say there is a loan that is going to be repaid in 30 days with weekly payments. That’s 4 weeks and 2 days. BTCJam says there are going to be 5 equal payments. Why are the two days considered a whole week? Same with a 365 loan, being repaid in 13 equal monthly payments. Why 13 and not 12?

I’m sorry if I sound like the biggest newbie around, I’m quite new to p2p lending and to loans as a whole.