This is question about Treasury Bonds Pricing. Can anybody explain about K calculation, why it starts from May - 16 days? Why not March/January or May - 31? You can see, Calculation "K" May - 16 days, June - 30 days, July - 15 days, July - 16 days, so on. I don't understand why they only show May - 16 days? Why it don't start from Jan - 31 days, Feb - 29 days, March - 31 days? Why it starts from May - 16 days? and also why only 16 days?

Example 1: A bond has a face value of $1000, pays 8% per annum with half-yearly coupons and matures on 15 November 2019. Assume that the bond was sold on 15 July 2015. Yields for similar Treasury bonds then were 7% per annum. Calculate: ink, C, P (price of the bond) Calculation of k: Month Total Days Number of days 61. May - 16 June July -15 July -16 August September October November -15 123 184 Example 1: A bond has a face value of $1000, pays 8% per annum with half-yearly coupons and matures on 15 November 2019. Assume that the bond was sold on 15 July 2015. Yields for similar Treasury bonds then were 7% per annum. Calculate: ink, C, P (price of the bond) Calculation of k: Month Total Days Number of days 61. May - 16 June July -15 July -16 August September October November -15 123 184