To calculate time to maturity, you'll need to know the bond's coupon rate and current market value. Then, you can use this formula:
Time to Maturity = (Coupon Rate / Current Market Value) x Number of Years to Maturity
For example, let's say you have a $1,000 bond with a 5% coupon rate that matures in 10 years. The current market value of the bond is $950. Using the formula above, we get:
Time to Maturity = (5% / 950) x 10 years = 0.526 years ≈ 6 months